REFERENCE MANUAL
OrthoVista 6.1
All rights to this publication are reserved. No part of this document may be reproduced, transmitted, transcribed, stored in a retrieval system, or translated into any language, in any form or by any means, without prior written permission from Trimble Germany. The software described in this document is furnished under a license agreement. The software may be used or copied only in accordance with the terms of the agreement. It is against the law to copy this software on magnetic tape, disk, or any other medium for any purpose other than the licensee’s personal use. Copyright 2001, 2015 Trimble Germany All rights reserved. OrthoVista Software Manual for OrthoVista Version 6.1 and higher Trimble Germany reserves the right to make changes to this document and the software described herein at any time and without notice. Trimble Germany make no warranty, express or implied, other than those contained in the terms and conditions of sale, and in no case is Trimble Germany liable for more than the license fee or purchase price of this product. Sample data “CastleRock” used in this manual provided courtesy of Digital Globe Incorporated. The sample imagery is of Castle Rock, Colorado U.S.A. The imagery has 5 m ground resolution and is in NAD83 UTM zone 13. Units are in meters.
1
Introduction to OrthoVista ........................................................ 1
1.1
Quick start ................................................................................................... 1
1.2
What is OrthoVista? ................................................................................... 1
1.3
Available Versions ..................................................................................... 1
1.4
What can OrthoVista do for you? ............................................................. 1
1.4.1 1.4.2 1.4.3
Manual or semi-automatic adjustments ................................................................. 2 Balancing and tilting .............................................................................................. 2 Mosaicking ............................................................................................................ 3
1.5
How does OrthoVista fit into your workflow? ......................................... 3
1.6
Will OrthoVista solve all your imagery problems? ................................. 3
1.7
How can you be trained in OrthoVista? ................................................... 4
1.8
Installing OrthoVista .................................................................................. 5
1.9
What are the system requirements for running OrthoVista? ................. 5
1.10
Windows installation.................................................................................. 5
1.10.1
Windows registration ............................................................................................. 5
1.11
Linux installation ........................................................................................ 5
1.11.1
Linux registration ................................................................................................... 6
2
Getting Started with OrthoVista ............................................... 7
2.1
Invoking OrthoVista ................................................................................... 7
2.2
Exiting OrthoVista ...................................................................................... 8
3
Basic Concepts ......................................................................... 9
3.1
Main window ............................................................................................... 9
3.1.1 Show Histogram .................................................................................................. 10 3.1.2 To Front............................................................................................................... 10 3.1.3 Display Layers ..................................................................................................... 11 3.1.4 Viewing Control ................................................................................................... 11 3.1.4.1 “Single-shot” versus “Continuous” mode: ..................................................... 12
3.2
Shortcuts ................................................................................................... 12
3.3
Language Selection ................................................................................. 12
3.4
Plugins ...................................................................................................... 13
3.4.1 3.4.2 3.4.3
Image support plugins (image formats) ............................................................... 13 Georeference data support plugins (report formats)............................................ 13 Image adjustment plugins (image processing) .................................................... 13
3.5
Rotated images ......................................................................................... 14
3.5.1
Rotation of output mosaic .................................................................................... 14
3.6
File management ...................................................................................... 14
3.7
Project Dialog ........................................................................................... 15
3.7.1 3.7.2 3.7.3 3.7.4
Mosaic ................................................................................................................. 16 Images ................................................................................................................ 19 Tiles..................................................................................................................... 20 Vectors ................................................................................................................ 21
3.8
Defining the processing area .................................................................. 26
3.8.1 Using a tile definition with simple parameters (standard file extension is tsp) ..... 26 3.8.2 Using an ESRI ARCshape file as tile definition ................................................... 29 3.8.3 Using an explicit tile definition file (standard file extension is txt) ........................ 30 3.8.4 Using a tile definition with simple parameters from a text editor (standard file extension is tsp)................................................................................................................. 30 3.8.5 Loading a tile definition file: ................................................................................. 33 3.8.6 Clipping to Area of Interest .................................................................................. 33
3.9
Loading input image data ........................................................................ 33
3.9.1 3.9.2
Background pixels ............................................................................................... 37 Display mapping .................................................................................................. 37
3.10
Specifying a custom area ........................................................................ 38
3.11
Selecting one or a group of tiles: ........................................................... 39
3.12
Begin Processing ..................................................................................... 40
3.13
Clearing the defined processing area .................................................... 40
3.14
Image Commander ................................................................................... 40
3.14.1 3.14.2 3.14.3 3.14.4
Generation of Overviews ..................................................................................... 41 RGB Channel Assignment .................................................................................. 41 Radiometrix ......................................................................................................... 42 View Image ......................................................................................................... 42
3.15
Radiometrix Editor ................................................................................... 42
3.15.1 3.15.2 3.15.3
Adjusting images with the Radiometrix Editor ..................................................... 42 Save/Reject changes of the Radiometrix Editor .................................................. 55 Radiometrix Editor: Background information ....................................................... 55
3.16
Color Picker .............................................................................................. 55
3.17
Status Dialog ............................................................................................ 56
3.18
“Move To…” Dialog .................................................................................. 56
4
Processing Options ................................................................ 57
4.1
Output options .......................................................................................... 58
4.1.1 4.1.2 4.1.3 4.1.4 4.1.5
Specifying the Output Directory ........................................................................... 58 Meta Data Directory ............................................................................................ 58 Output Image format ........................................................................................... 59 Output Report format........................................................................................... 60 Save Background Information for Output Images ............................................... 61
4.2
Adjustment options .................................................................................. 61
4.2.1 Specifying radiometric adjustments for single images ......................................... 61 4.2.2 Per-Image Selection ............................................................................................ 64 4.2.3 Image group adjustment ...................................................................................... 64 4.2.3.1 Global Tilting Adjustment ............................................................................. 65 4.2.3.2 Contrast adjustment options......................................................................... 67 4.2.3.3 Reflections Removal .................................................................................... 69 4.2.3.4 Per Image Selection ..................................................................................... 71 4.2.4 Mosaic adjustment .............................................................................................. 71
4.3
Output Selection ....................................................................................... 76
4.3.1 Saving adjusted images ...................................................................................... 76 4.3.2 Generate Seam Data (*.cld Files)........................................................................ 76 4.3.3 Save Vector Seams............................................................................................. 77 4.3.4 Save Vector Seams for each image .................................................................... 77 4.3.5 Seam simplification tolerance .............................................................................. 77 4.3.6 Save Mosaic Output ............................................................................................ 77 4.3.7 Options for Saving Adjusted Images and Mosaic Output .................................... 77 4.3.7.1 Internal Name of Output ............................................................................... 78 4.3.7.2 Directory ....................................................................................................... 78 4.3.7.3 File Name Format ........................................................................................ 78 4.3.7.4 Ratio ............................................................................................................. 78 4.3.7.5 Number of channels and RGB component setting ....................................... 78 4.3.7.6 Channel assignment .................................................................................... 78 4.3.7.7 Example for 4 Channel RGB and Infrared image ......................................... 79
5
Advanced Information ............................................................ 81
5.1
Multi-Channel Image Support ................................................................. 81
5.2
Batch Mode Processing Capabilities ..................................................... 81
5.2.1
Examples ............................................................................................................ 82
5.3
Using user-defined vectors ..................................................................... 82
5.4
Radiometric Models ................................................................................. 83
5.5
Hot spot removal ...................................................................................... 85
5.6
Intensity Dodging ..................................................................................... 85
5.7
Coordinate reference ............................................................................... 86
5.8
Non constant pixel size, odd offset of orthophotos and tiles .............. 86
5.8.1 5.8.2
Non constant pixel size ....................................................................................... 86 Odd offsets .......................................................................................................... 87
5.9
Processing large blocks .......................................................................... 88
5.9.1 5.9.2
Two step processing ........................................................................................... 88 Subdividing a block in sub-blocks........................................................................ 88
5.10
Processing speed ..................................................................................... 89
6
End User License Agreement................................................. 91
Reference Manual OrthoVista
1
Introduction to OrthoVista
1.1 Quick start Here’s a guide that refers you to sections of the manual that will get you started quickly with OrthoVista: If you already have OrthoVista installed and running, you can use icons found on the toolbar to guide you through the three simple steps to processing image data with OrthoVista: Load image data. This icon invokes the Choose Directory dialog so that you can specify the location of your input data and load the imagery for processing. Select processing area. This icon invokes the Custom Area dialog where you can define the image area to be processed. You can select all images or use your mouse to define a processing area. Process imagery. This icon invokes the Processing Options dialog. Simply specify an output directory, adjust any processing options if necessary and click the Process button.
1.2 What is OrthoVista? OrthoVista is a powerful software product that improves the quality, utility and value of ortho-rectified, digital image mosaics by performing a series of radiometric adjustments designed to match color and intensity across component images and producing seamless image mosaics.
1.3 Available Versions OrthoVista is available in a Full, Lite and Education version. OrthoVista Lite is considered being a small business solution for small companies dealing with smaller projects. The lite version can easily be upgraded to the full version by just changing the license on the dongle. The lite / education versions have the following limitations:
Up to 250 images or 12 pushbroom images can be processed in one project
Parallel processing limited to two processes/threads
No batch-processing
1.4 What can OrthoVista do for you? OrthoVista computes radiometric adjustments that compensate for visual effects such as hot spots, lens vignetting and mismatches between adjacent mosaic images. In addition it offers a powerful set of tools to manipulate the radiometry of Page 1
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single or group of images. Finally OrthoVista automates production of high-quality, photogrammetric orthophoto mosaics, providing the capability to define mosaic production quickly and easily on a project-wide basis.
Figure 1: Sample data set before OrthoVista processing.
1.4.1 Manual or semi-automatic adjustments The built-in Radiometrix tool offers a set of tools to correct gradation, intensity, contrast, color and saturation, both manually and semi-automatically. Additional tools for selective color correction in hue, saturation and lightness as well as the possibility to record a macro have been added. Besides the functions in the Radiometrix Editor, tools like the histograms and Color Picker can be used to check the changes.
1.4.2 Balancing and tilting OrthoVista removes solar reflection “hot spots” and improves visual uniformity of most orthophotos by balancing the intensity and color variation across each frame. The software compensates for lens vignetting and various illumination effects by matching the color and intensity of adjacent input images in order to provide smooth and consistent radiometric image properties across all images. OrthoVista can correct color and intensity defects introduced during scanning or other processing as well. Further on water reflections can be eliminated and images can be interactively changed in color, brightness, contrast and saturation.
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Figure 2: Sample data set after OrthoVista processing
1.4.3 Mosaicking OrthoVista can be configured to generate seamless image mosaics from large numbers of individual orthophotos for use in Geographic Information System (GIS) and remote sensing applications.
1.5 How does OrthoVista fit into your workflow? OrthoVista works with digital orthophotos in standard formats. The imagery produced by OrthoVista is immediately ready for delivery to clients or applications that use orthophoto mosaics. OrthoVista processes the individual orthophoto images and accompanying geodetic information that are typically produced by a soft-copy photogrammetric workstation or an orthophoto production system. Because processing can be performed in the background or after hours, OrthoVista can dramatically increase production efficiency.
1.6 Will OrthoVista solve all your imagery problems? While OrthoVista does an excellent job of performing radiometric corrections for a majority of the imagery that’s processed, there will always be extreme cases that automated image processing cannot address satisfactorily. Likewise, while OrthoVista will produce seamless mosaics most of the time, you may encounter problems with some cases involving exceptionally demanding imagery. Here are some specific issues that may be encountered during radiometric correction and mosaic production: Page 3
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Definition of background pixels. By default OrthoVista treats 0,0,0 as background. You can modify OrthoVista’s interpretation of background values. See the “Setting Preferences” for information on manipulation of background pixel values. Processing Options). This will promote a more stable solution, but will leave “hot spots” in unbalanced imagery. Another option is to define an area to be excluded from processing as discussed in the chapter 3.7.4 Vectors. Contrast adjustments. Severe contrast differences between adjacent images can result in a detectable visual difference between images. Radiometric adjustments have two methods (multiplicative and additive), which have different contrast effects. Experimenting with these methods may show that selecting one method may provide better results than the other for a given set of images. An effective approach is to manually adjust the contrast of input images that have extremely disparate contrast properties with the use of the OrthoVista Radiometrix Tool. Trimble is committed to improving and enhancing OrthoVista. The software is continually addressing more of these demanding situations and will get better and better at handling problematic data; however, it’s important to note that results may not be “perfect” when dealing with particularly difficult imagery.
1.7 How can you be trained in OrthoVista? To get a quick start in using and understanding OrthoVista we offer an online training package “OrthoVista I Tools & Functionality”. Closer information you can find at Learning Center (http://learn.trimble.com/lms/)
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Furthermore we offer on-site trainings either at your place or here in Stuttgart. We are pleased about your interest. Contact us at
[email protected]
1.8 Installing OrthoVista To install OrthoVista, load your distribution DVD-ROM or download an archive file from the OrthoVista download page on the Inpho or Trimble Geospatial website: http://www.inpho.de or http://www.trimble.com/geospatial/aerial-software.aspx
1.9 What are the system requirements for running OrthoVista? Processing time is determined mainly by CPU speed and even more important disk access speed. OrthoVista requires a 64bit operating system with at least 4GB RAM. Always try to run OrthoVista with image data on fast, local disk storage device. Should you use network drives, we strongly suggest to always map the network drives, use a 1 Gbit network or even faster otherwise the processing performance will be severely affected.
1.10 Windows installation Just start the setup.exe and follow the installation instructions.
1.10.1 Windows registration OrthoVista uses a hardware dongle to protect the software. You will get the dongle when you purchase OrthoVista. It is also possible to run OrthoVista with a server license where the dongle is managed and located on a server accessible via the network.
1.11 Linux installation You will find a detailed description in the Installation.pdf
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1.11.1 Linux registration Starting with version 4.3 of OrthoVista, the Linux version of our software uses hardware licensing via WIBU CodeMeter. This requires that the CodeMeter software is installed and running on any computer that should run the software, even if the license is acquired over the network. The latest version of the CodeMeter runtime is always available under: www.codemeter.com For convenience, the current version is bundled with this software. Installation files for Debian based systems (Debian, Ubuntu, ...) can be found under opt/inpho/deb-packages, those for rpm based systems (SuSE, RedHat, ...) can be found under /opt/inpho/rpm-packages. Both directories contain subdirectories for 64bit systems (amd64 or x86_64). Please pick the appropriate installer package for your system and install it as usual. After installation, you might delete the directories /opt/inpho/deb-packages and /opt/inpho/rpm-packages.
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2
Getting Started with OrthoVista
2.1 Invoking OrthoVista To start OrthoVista, use one of the following instructions: On Windows systems, double-click the OrthoVista icon. On Linux systems, type orthovista (or the alias you’ve assigned) at any command prompt. (Remember that Linux is case-sensitive.)
Figure 3: The OrthoVista Main Window and Project Dialog Once started, OrthoVista displays its main window and the project dialog. Using the software generally involves three simple steps that can be initiated using the icons below available in the main window’s toolbar: Load image data. This icon invokes the Choose Directory dialog so that you can specify the location of your input data and load the imagery for processing. Select processing area. This icon invokes the Custom Area dialog where you can define the image area to be processed. You can select all images or use your mouse to define a processing area. Process imagery. This icon invokes the Processing Options dialog. Simply specify an output directory, adjust any processing options if necessary and click the Process button. Refer to the OrthoVista Tutorial for more help getting the software up and running quickly. To start using OrthoVista, you need georeferenced image data. This data must consist of individual orthophoto images and accompanying geodetic reference information. Page 7
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OrthoVista works with a variety of georeference data generated by common mapping, remote sensing, photogrammetry and image processing software. Orthophoto data typically are produced using a soft-copy photogrammetric workstation, an orthophoto production system and/or various remote sensing software packages.
2.2 Exiting OrthoVista To quit OrthoVista: Select Quit from the File menu.
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3
Basic Concepts
3.1 Main window OrthoVista provides a number of tools that control the way in which your imagery is displayed in the main window.
Figure 4: Main window Once you’ve loaded your image data, you can manipulate the display using either: The icons displayed on the left side of the main window. The Display Layers pop-up menu.
Figure 5: Display Layer Popup Menu To activate the Display Layers pop-up menu, right-click in the main window and hold the mouse button down for at least 1 second. Page 9
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Note: The layer “Editing” is not used in OrthoVista, as it toggles the currently digitized seamline while editing.
3.1.1 Show Histogram To display histograms of single images, right-click on a certain image and hold the mouse button down for at least 1 second. A pop-up menu allows you then to open the histogram of this image.
Figure 6: Image histogram
3.1.2 To Front If images overlap each other at a certain position, OrthoVista displays the last loaded image on top of all the others. To change the sequence of images, rightclick on a certain position and hold the mouse button down for at least 1 second. A pop-up menu allows you then to select a certain image which will be then on top of all others.
Figure 7: Selection of an image to be on top
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3.1.3 Display Layers The Display Layers Tool Bar contains a number of tool buttons to toggle the display. Each option can be turned on and off independently.
Images: Displays the input images within the ortho borders. Ortho Borders: Displays the borders of the input images in red. Tile Borders: Displays the tile definition borders, if any are defined. Output Areas: Displays the physical area (Tiles) to be processed. Seams: Displays seam polygons in Seam Editor, does not display any information in OrthoVista itself. User Vector Data: Displays the borders of loaded user vector data like exclusion areas, seam areas and water areas. Names Display: Displays names of images and tile definitions.
3.1.4 Viewing Control The View Control Tool Bar contains a number of tool buttons used to change the area displayed in the Main Window.
Zoom window mode: This is the standard mode for zooming. By clicking and holding the left mouse button, drag a rectangle over the desired view area. Release the left mouse button, and the view display will zoom to the defined area. A single right click will zoom back to the previous zoom level. Note: If the zooming rectangle is too small, no zooming will take place. To zoom into a tiny rectangle, you might have to use two subsequent zooms. Panning mode: When panning is active, you can ‘grab’ the image shown in the Display Area and drag it to a new position. This is similar to using the scrollbars of the Display Area. See also 3.1.4.1. Zoom-in mode: While in this mode, each click with the left mouse button will recenter at that location and also zoom in by a factor of two. A single right click will zoom back to the previous zoom level. See also 3.1.4.1. Zoom-out mode: In this mode, each click with the left mouse button re-center at that location and also zoom out by a factor of two. A single right click will zoom back to the previous zoom level. See also 3.1.4.1. Zoom reset button: This button resets the zoom stack and shows the whole project in a ‘fit-to-view’ zoom level. Page 11
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3.1.4.1 “Single-shot” versus “Continuous” mode: The panning and the zoom in/out buttons operate in two different modes. A single click on the button involves a single-shot operation. Once this operation is activated the view control falls automatically back to the “zoom-window” mode. Double clicking these buttons enters the modes permanently until a different zoom/pan button or the zoom-window button is pressed.
3.2 Shortcuts Zooming, panning and window sliders can be also controlled by using hard-key shortcuts. The following shortcuts are supported: Shortcut + F C Arrow Keys
Function Zoom in Zoom out Full Screen or Reset Display Center Position Move Slider up/down/left/right
3.3 Language Selection OrthoVista supports multiple languages for the user interface and messages. In addition to English (the default language) there is support for German, Russian, Spanish and Chinese, other languages may follow. The current language may be selected using the Language Selection Dialog, available in the Setup menu (second from left, in case you are unable to read the entries in the current language) as item “Language…” (second from bottom):
The language dialog searches for language files installed on the system and offers all available languages in the drop-down box. To pre-set the language for all users of the system, the application has to be started with administrator privileges and the checkbox has to be activated. Support for other languages may be added independent of the software and may be provided by third parties. Please contact our support team if you are interested in providing an additional language. The OpenGL font setting is not used in OrthoVista and Seam Editor, this setting should be left unchanged. Page 12
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3.4 Plugins OrthoVista supports an innovative architecture that packages specific product functionality into modules called “plugins.” The advantage of using a modular architecture is that OrthoVista only loads the modules required to perform the processing jobs that you specify resulting in faster, more efficient processing. Plugins support third-party development and product customization. They encapsulate product features such as image format support and specific image processing capabilities. This allows independent development and delivery of schedule-critical and/or proprietary processing modules. Plugins are grouped into several categories; you can get details on each specific plugin from OrthoVista’s Info menu.
3.4.1 Image support plugins (image formats) OrthoVista accepts a variety of image formats: TIFF (scanline or tiled) and GeoTIFF JPEG (read only, limited to 51MPixel uncompressed image data) ADS (uncompressed and TIFF/JPEG, no hardware compression) BigTIFF (scanline or tiled) BIP/BIL/BSQ To determine which specific image formats are supported by your installation of OrthoVista (e.g., list the image support plugins that are currently installed), select About Plugins from the Info menu and select Image Support Plugins. A dialog will display the plugins currently available and provide detailed technical information about image formats and their specifications.
3.4.2 Georeference data support plugins (report formats) These plugins are used to read and write image georeference information. GeoTIFF .tif format Worldfile .tfw and .tifw (for TIFF images), .jgw, (for JPEG images) and .bpw, .blw, and .bqw (for BIP/BIL/BSQ images) formats Vision Softplotter .rpt format Zeiss Phodis .inp format ER Mapper raster file format .ers GeoTIFF Note: OrthoVista handles GeoTIFF files that contain the image and header data in the same file, and supports the following tags in GeoTIFF format: ModelTiepointTag ModelPixelScaleTag ModelTransformationTag Other tags that describe projections as well as extensions that are not supported will be carried through the process and written in the output files without alteration. More information concerning GeoTIFF can be obtained from OrthoVista’s Info menu.
3.4.3 Image adjustment plugins (image processing) Many of OrthoVista’s processing capabilities are implemented as plugins: hot spot removal intensity dodging Page 13
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global tilting adjustment reflections removal mosaic space resampling plain mosaicking sheet centered mosaicking adaptive feathering feature detection seam applicator Check the Info menu to determine the plugins currently installed. Custom plugins may also be developed to meet an individual customer’s specific image processing requirements.
3.5 Rotated images OrthoVista can accommodate rotated input images. It can also rotate the output image so that mosaics are generated with arbitrary pixel row/column azimuths. If all input images are not aligned, then image sampling is required. OrthoVista applies a bilinear resampling using existing image pyramids. Consequently, processing of rotated images can be substantially slower than processing nonrotated imagery. OrthoVista automatically detects input image rotation when it reads the input orthophoto georeference data.
3.5.1 Rotation of output mosaic Use the mosaic space specification, available in the project dialog. For further information, please refer to chapter 3.7.1 Mosaic. The canvas orientation button represents the North Direction.
3.6 File management
Create a new project: Creates a new project and clears data that was previously loaded in OrthoVista. Open an existing project: Displays a file selection dialog where you can select and load an existing project. Save the current project: The project itself and the selected processing area respectively tile definitions are written to disk. Imports a “Configuration File”. The configuration is imported and written into the orthovista.cfg file located on the directory “C:\Documents and settings\All Users\Application Data\Trimble\Inpho5\Settings” (on Windows 2000 and Windows XP) respectively “C:\ProgramData\Trimble\Inpho5\Settings” (on Windows Vista/7).
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Saves the parameter settings into a user defined “Configuration File”. Printing the display OrthoVista allows you to print what appears in the main window. You can output to printers and/or postscript files. To print the current display: Select Print Display from the File menu. The printed output represents what is on the screen, so zooming and scrolling the main window will change what is printed. For best results, resize the main window to match the proportions of the page to which you are printing.
3.7 Project Dialog The project dialog allows parallel to the handling in the main window, four additional options: Mosaic: for resampling and rotations Images: for image handling Tiles: for loading, defining and selecting tiles Vectors: for vector data handling The selection of the meta data directory is listed in all 4 tabs.
The project dialog includes also some information about the number of loaded images, the usability and the activation/deactivation status of the images. This information is located in the lower left corner of the project dialog.
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3.7.1 Mosaic
The Mosaic Space Specification allows resampling the input data and aligning it to a new reference point. The reference point is always referring to the corner of the pixel, not the center of the pixel. For resampling, the bilinear resampling using existing pyramids will be applied. Note: changing the mosaic space specification requires a new tile definition and selection. Therefore please change mosaic space specifications, prior to the tile definition and selection. OrthoVista rotates the view of the input images. Tile definitions and selections are always displayed parallel to the main window. The main window stays aligned with the output mosaic. The specified angle is represented with the canvas icon in the lower left corner of the main window. The below graphics explain the display of the project in main view for a nonrotated project in comparison to a rotated project: Non-rotated images:
Imported orthos, pointing north Defined tile definition, always parallel to main window Axis of main window Orientation angle of 0 degrees for output tiles Page 16
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Canvas, showing the north direction
Rotated images:
Imported orthos, pointing north Defined tile definition, always parallel to main window Axis of main window Orientation angle of 20 degrees for output tiles
Canvas, showing the north direction 20 deg Automatic: The existing georeference (Reference Point) of one image will be used and all others will be resampled accordingly. Defined by Reference Point, Angle and Pixel Size: Allows defining manually a new reference point, a rotation and a pixel size Defined by Reference Point and Unit Vectors: Allows defining manually a new reference point and unit vectors like in a TFW file Reference Point (pixel corner): This option allows defining manually a new reference point (X and Y) that should be used for resampling. Column Vector: Defines the column vector in X and Y. The values refer to the first and second entry in the TFW file: 0.100000 0.050000 0.050000 -0.100000 Page 17
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2571491.475000 5647965.975000 Row Vector: Defines the row vector in X and Y. The values refer to the third and fourth entry in the TFW file: 0.100000 0.050000 0.050000 -0.100000 2571491.475000 5647965.975000 Angle: The angle can be keyed in to define the rotation of the output images. In case the “Defined by Reference Point and Unit Vectors” option is used, the resulting angle value from the column entry is displayed. Pixel Size: Allows defining a new output pixel size. This option can be used to down sample images to a specific ground sample distance (GSD) or to unify varying GSDs to one size. Changing the pixel size will result in resampling of the images. Apply Changes: Applies the changes and updates the main window. In case apply changes is not used, the main window might represent different values compared to the defined mosaic space specification. Pending Changes and Active Settings: To avoid confusion and misunderstanding, the dialog shows always the “pending changes” before applying them to the project and the current “active settings” which are being represented in the main window.
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3.7.2 Images
Loading orthophotos by file or directory Like in the main menu, the project dialog allows to load either single or a group of files or a whole directory. See also chapter 3.9. Unload selected images allows to unload images after they are selected first in the project dialog. Change file path allows changing the file path of images after they are selected first in the project dialog. This function is needed after having loaded a project file and the file path of the images in the project file is no more correct. To change the path, select images first, press the Change Path button select a directory. The new directory will then be automatically applied.
to
The meta data directory can be changed as well by using the Browse button. Activating/Deactivating images allows activating/deactivating images after they are selected first in the project dialog. Only activated images are displayed in the main menu and processed. Select/Unselect images allows selecting/unselecting images for the Radiometrix Editor after they are selected first in the project dialog. The columns in general represent the status of individual images Name
Lists the image name
Georeference Checks for information about the georeference. The tool tip Page 19
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window for a georeference entry shows some additional information about the image’s georeference. Image
Is the image online? The tool tip window shows some additional information about the raster image.
Usable
Can the image be used and is e.g. not corrupt?
Active
Lists the activation/ deactivation status of the image
RDX sel.
Lists if an image is selected for radiometric changes in Radiometrix Editor
Single
Lists if the image has been activated for single image adjustment
Group
Lists if the image has been activated for Image group adjustment
Output
Lists if the image has been selected for output of adjusted images
3.7.3 Tiles
Load tiles allow loading tiles from a tile definition file. See also Chapter 3.8. Create a new tile definition file allows creating a new tile file (*.tsp). See also Chapter 3.8. Edit selected tile definition allows editing the select tile definition file (*.tsp). See also Chapter 3.8. Unload tiles allows to unload a tile file after being selected in the project dialog.
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Mark/unmark tiles for processing allows to mark/unmark tiles for processing after they are selected first in the project dialog. Mark all edited tiles for processing. Clear the edited status of all tiles selected in the project dialog. The Edited status is automatically modified by the Seam Editor when seam lines influencing a certain tile are modified. Once seams are modified with the Seam Editor the changes have to be applied with a Seam Applicator run. In order to avoid that all tiles have to be reprocessed, the Edited status helps to check which tile has to be re-processed. The Tiles list can be sorted for Edited and non-Edited tiles and once sorted the tiles can be selected and marked for processing. If further on seams are modified it is helpful to set the tile status back to not-Edited before starting a new Editing.
3.7.4 Vectors
The vectors tab in the project dialog provides all functions for the vector file handling. Compared to previous versions, the vector file handling has been removed from the HotSpot Removal, the Reflections Removal and the Building Outline functionalities and is located centralized in the vectors tab in the project dialog. Load vectors from file allows loading vector data files for further usage. Supported formats are AutoCAD DXF and ESRI ARCshape. There is no naming restriction as the type of the vector layer needs to be assigned in the vector layer properties. Note: Vector data is not imported into the OrthoVista project file. The project file only contains a reference to the original vector data file. Take care not to remove vector data files you need to be available in OrthoVista or the Seam Editor. Page 21
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Edit the selected vector layer settings: allows assigning and modifying the layer usage, type, complex polygon status, visibility and color. Depending on the layer usage, options and default settings will change.
File Name: Lists the name of the loaded file. This entry cannot be modified. Layer Name: Lists the name of the selected layer. This entry cannot be modified. Layer Usage: Allows the selection of the layer usage. Options are: Ignored: Files and Layers can be loaded for display purposes only. Layers will not be used during processing. Hot Spot Removal: OrthoVista can skip radiometric balancing to the area within a polygon that is used for the Hot Spot Removal function. Polygons are typically used as exclusion areas for the radiometric correction. Please see the table below for further details. Area of Interest: This function allows loading one or several polygons which can be used as project boundary. Clipping the block to a specified area can be utilized as inclusion or exclusion area. Generated Seam: Seamlines being generated in a previous OrthoVista run can be loaded for visualization purposes. Building Outlines: Building outlines mark exclusion areas for seam lines. The automatic seam
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line finding functions (Feature detection) will then avoid these areas. Import of closed polygons in DXF and SHP format are supported. Note: If an exclusion area covers the complete overlap, the seam line may go straight. Reflection Area: Polygons describing the water area have to be used for the removal of reflections on water bodies. It is necessary to define the Reflection Areas with closed polygons. Several areas can be defined. If a defined area is within another area, the inner area defines an island which is then treated as an exclusion area for the Reflection Removal. Currently the Reflection Areas must be imported via a DXF file or ArcShape file. Please see below table for further details on the layer usage options. Layer Type: Allows the selection of the layer type. Options are: Lines, Inclusion and Exclusion. Please see below table for further details. Complex Polygon: When the option “Complex Polygon” is set to status “yes” then the import routine analyses all the polygons. To skip the analysis, the polygon definition needs to fulfill two requirements: (1) The polygon must not be self-intersecting, i.e. there must not be any line segments that intersect each other. In case partly overlapping areas are found, they are merged together to one common polygon if the “Allow Complex Polygon Definition” is switched on.
Figure 8: Two polygons overlapping
Result “Complex Polygon” activated
(2) The vertex order of the digitized polygons for Reflection Area is important. Water Area Land Area/Islands
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Figure 9: Recommendation: Water area digitized counter-clockwise If the status of “Complex Polygon” is set to “no”, the direction how polygons are digitized is important. In this case digitize the outer water areas counter-clockwise and all islands clock wise. If a polygon with the type “left exclusive” is used, then the water area may also be digitized clockwise and the islands have to be digitized counter-clockwise. If the polygon definition does not satisfy both requirements, the status of “Complex Polygon” must be set to “yes. Note: In case of “Complex Polygon” - for large Reflection Area Definition files the analyzing can take a considerable time (several hours). In case partly overlapping areas are found, they are merged together to one common polygon. So enable this option only if you would like to combine polygons to one and you don’t like to consider the digitization direction. Layer Visibility: Allows to activate the layer display in the main window. Please note that visualizing larger files in the main window might take several minutes. It is not necessary for the processing to activate the display of the vector layers in the main window. Files are being used for the selected processing as long as soon as the layer usage is selected. Layer Color: Allows changing the display color of layers in the main window. Default colors are: Hot Spot Removal: purple Area of Interest: green Generated Seam: Building Outlines: red Reflection Area: blue Unload selected vector file allows unloading selected vector data files. Unloading single layers from a vector file is currently not supported. Changes the file path for selected vector files: allows modifying the path of already loaded vector data files, in case file locations have been changed. Layer Usage ignored
Layer Type Lines Inclusion Area Exclusion Area
Description Files and Layers can be loaded for display purposes only. Layers will not be used during processing.
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Hot Spot Removal
Inclusion Area
Digitized Polygon Hot Spot Removal corrected Area Non-corrected Area
Exclusion Area
Digitized Polygon Hot Spot Removal corrected Area Non-corrected Area
Area of Interest
Inclusion Area
Digitized Polygon Output Area Clipped Area
Exclusion Area
Digitized Polygon Output Area Clipped Area
Generated Seam
None
Loaded Seamline Display Background color
Building Outlines
None
Reflection Area
Inclusion Area
Files and Layers can be loaded for display purposes only. Layers will not be used during processing. Polygons representing building outlines are treated automatically as exclusion areas for the seamline detection (Feature Detection algorithm only) Digitized Polygon Land Area Water Area
Exclusion Area
Digitized Polygon Land Area Water Area Page 25
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3.8 Defining the processing area For your convenience, you can define specific areas of the input image data for processing. Each area defines an output file. Radiometric corrections are only computed for the areas that are defined by the collection of all processing areas. OrthoVista’s processing does not include images whose area is not included in a defined processing area. A common first step in production operations is to create a tile definition file. Often, the output tile definition is created during flight planning or project management activities. OrthoVista can read tile definition files and use them to define output mosaic boundaries. The following sections describe alternative techniques to define the image processing areas.
3.8.1 Using a tile definition with simple parameters (standard file extension is tsp) To create this form of a tile definition file, use tile definition creation dialog from the Project Dialog window. First step is then to define a tile definition file first. All changes defined in the tile definition menu are then directly applied to the stored tile definition file. Note: The images must be loaded before defining the tiles. The tile definition has to know pixel size and image location to work correctly.
Reference Point The Reference Point can be either keyed in or picked in the main window using the left mouse button. It describes the Page 26
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East/North of any exact corner. The aligned to information displays the coordinates rounded according to the loaded georeference of the images. Please note that the output tiles will be generated according to the aligned value. Tile Size The Tile Sizes are X(E-W) and Y(N-S) tile dimensions in ground units, e.g. meter. The aligned to information displays the coordinates rounded according to the loaded ground sample distance of the images. Please note that the output tiles will be generated according to the aligned value. Tile Skip The Tile Skip is optional and can be used to define overlapping tiles. Tile Count Tile Count specifies for each direction (east, west, north, and south) the quantity of tiles starting at the reference point. Name Pattern The name pattern editor can be used to automatically create output file names for the tiles. Name patterns may include coordinate values (east, north), incremental indices (east-west, south-north) or simple text. Make sure that no duplicate names for the tiles are being generated. Name Pattern Editor
Add Select a new name pattern (coordinate values, incremental indices or text). Edit Edit existing patterns. Remove Remove existing patterns Up/Down Page 27
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Defines the order of the name pattern. Up and down can be used to change the existing name pattern order. The pattern fields can have the following values: Coordinate
Direction indicator: Select whether the x or y coordinate is to be written to the name pattern string. Reference specifier: Define if the coordinates shall be displayed for the ceter or for one of the four tile corners Trim to field width: Define the field width Truncate by: Truncate by a number of digits to cut off the last digits ofa coordinate value Pad with leading zeros: Fills the specified field width with leading zeros if the coordinate value is too small. Index
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Direction indicator: To name the output tiles with incremental indices, define the direction indicator whether index number of the 1st, 2nd… tile from east to west or from north to south is to be used. Trim to field width: Define the field width for the index numbers. Pad with leading zeros: Fills the specified field width with leading zeros if the index number is too small Text
Text: Any explanatory comment can be written to the name pattern. Apply The Apply button overwrites existing tile definitions in the OrthoVista Project Dialog and automatically stores the changes in the earlier defined *.tsp files.
3.8.2 Using an ESRI ARCshape file as tile definition An ESRI ARCshape file defining the tile extents and names can be imported. The file can be generated using different software packages like the DTMaster. Important is the following specifications are being fulfilled: - The ARCshape file must contain polygons - The associated database must contain a column called NAME of type C(haracter). The database may contain other columns also - For each polygon there needs to be a corresponding database record where the content of the NAME column defines the tile name – the database must not contain other records - The order of the polygons in the file must match the order of the database entries defining their name - No duplicate tile names are allowed - Currently limited to maximum 10 000 polygons per file. In case files >10 000 polygons need to be loaded, the shp tile definition needs to be split in different files.
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3.8.3 Using an explicit tile definition file (standard file extension is txt) To create this form of tile definition file, use any text editor, spreadsheet, or processing script to write an ASCII .txt file in the format below. OrthoVista ignores lines where the second column has double quotes ( e.g., “”). The file consists of data in five columns: ascii string floating point number floating point number floating point number floating point number A sample file might look like this: "TileID" "NWx" "NWy" "SEx" SEy" "tile-A1" 470000 4510000 480000 4500000 "tile-A2" 480000 4510000 490000 4500000 : : These files are read by a tile definition plugin. Select About Plugins from the Info menu to determine the tile definition plugins supported by OrthoVista and to obtain detailed specifications for each format.
3.8.4 Using a tile definition with simple parameters from a text editor (standard file extension is tsp) To create this form of a tile definition file, use any text editor, spreadsheet, or processing script to write an ASCII .tsp file in the format below. File is a 'keyword value(s)' format with content: NOTE: Keywords INCLUDE the ':'(colon) character!
-----------#Everything after a '#' character is comment TileCorner: x0 y0 TileSize: dX dY TileSkip: dX dY TilesToWest: nXW TilesToEast: nXE TilesToNorth: nYN TilesToSouth: nYS TileNameFormat: fmt # end of file -----------Where: : x0, y0 : are East/North of any exact corner : sizeX, sizeY : are X(E-W) and Y(N-S) tile dimension : dX, dY : are X(E-W) and Y(N-S) distance between tiles : nXW : number of tiles to west of corner : nXE : number of tiles to east of corner : nYN : number of tiles to north of corner : nYS : number of tiles to south of corner : fmt : format for the output file names (see below) Page 30
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TileSkip is optional and defaults to TileSize and can be used to define tiles, which overlap each other. TileNameFormat is optional. The default is a row and column based numbering that guarantees unique tile numbers. Example: #----Start of File # place tiles on even 10k grid # NOTE: all units are 'world/ortho' units TileCorner: 120000 1320000 TileSize: 10000 10000 # assume corner is upper left (N/W) of project area # and that project area is covered by 5 by 7 tiles # but we also want to pad one extra column to the west # NOTE: units are 'number of tiles' TilesToWest: 1 # pad one column west of corner TilesToEast: 5 TilesToNorth: 0 # no rows above corner TilesToSouth: 7 TileNameFormat: t%03.3ulx%03.3uly #----End of File NOTE: numbers are expressed in decimal notation (e.g. the decimal is represented by a '.'(dot) character. Do _not_ use ','(comma) characters! Format String Description: A format string can be an arbitrary string that contains placeholders for tile specific information. The placeholder structure is as follows: Structure Option 1: a '%' sign an optional '0' (leadingZeroIndicator) an optional number (fieldWidth) the character 'e' or 'n' (eastNorthIndicator) Structure Option 2: a '%' sign an optional '0' (leadingZeroIndicator) an optional number (fieldWidth) an optional '.' followed by a number (cutLength) 'ul', 'ur', 'll', 'lr', or 'c' (cornerSpecifier) the character 'x' or 'y' (rightUpIndicator) The first structure is to include the horizontal ('e') or vertical ('n') tile number. It is printed using up to 'fieldWidth' digits. If there is a 'leadingZeroIndicator', there are exactly 'fieldWidth' digits; missing digits are padded with 0. Given the horizontal tile number 13, '%3e' gives '13', while '%05e' gives '00013'. The second structure is used to include the X ('x') or Y ('y') coordinate of a tile corner or the center in the tile name. The 'cornerSpecifier' is 'ul' for the upper left corner, 'ur' for the upper right corner, 'll' for the lower left corner, 'lr' for the lower right corner, and 'c' for the tile center. 'fieldWidth' - as above - specifies the Page 31
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maximum number of digits in the output, and 'leadingZeroIndicator' also behaves as described above. In addition, 'cutLength' gives the number of digits to be truncated from the right after rounding the coordinate value. Example: Assume the x coordinate of the upper left corner is 167874.738. First this is rounded to integer, giving 167874. A placeholder structure '%ulx' will thus result in '167874', '%8ulx' gives '167874', and '%08ulx' results in '00167874'. If 'fieldWidth' is less than the number of digits, digits are truncated at the left. For our example, '%4ulx' results in '7874'. To truncate from the right, 'cutLength' can be used. Thus '%.2ulx' gives '1678'. A combination might be '%2.3ulx', which results in three digits cut from the right, then taken the rightmost 2 digits: '67'. One more example: assume your coordinates are in meters, and you want a threedigit kilometer value of the lower left corner. The tile name must have the prefix 't_' and the X and Y values have to be marked with 'E' and 'N'. The format string for this tile specification is 't_%3.3llxE%3.3llyN'. For a lower left corner of (7521344.0 ; 13557412.0) the tile name will be 't_521E557N'. Example with TileSkip: TileCorner: 10000 TileSize: 1000 TileSkip: 900 TilesToWest: 1 TilesToEast: 1 TilesToNorth: 1 TilesToSouth: 1
10000 1000 900
Above settings lead to following tile corner coordinates:
11000/10900
9100/10900
10000/10000
9100/900
11000/9000
Figure 10: Example with TileSkip definition.
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The corners of the tiles are computed as follows: The given TileCorner defines the upper left corner of one tile (shaded tile). There are no more tiles to be generated to the south – east as the one already defined To the north – east, north – west and south – west the TileSkip value of 900 units is added and then an area of 1000 by 1000 units is defined. See tiles 11, 12, 22 so that the tiles overlap each other by 100 units. TileSkip defines the skipping distance from upper left corner to the next corner in x and y. At this corner then an area of TileSize dx, dy units is defined.
3.8.5 Loading a tile definition file: Select Load Tile Definition from the Setup menu. OrthoVista displays the Open dialog. Locate and select your tile definition file and click OK. OrthoVista displays the tiles you’ve defined in blue. Note: - TileSpec files must have the file extension “tsp” - Explicit tile definition files can have the file extension “shp” or “txt”.
3.8.6 Clipping to Area of Interest Tile definitions and selections can additionally be used with the “Area of Interest” option, to clip the output area to a predefined polygon. For further information, please refer to chapter 3.7.4 Vectors
3.9 Loading input image data To process your input image data, you need to specify the location of the inputimage data along with the georeference data (e.g. tfw). The image-data files and the georeference data files must be in the same directory. Note that all the georeference data files found in the directory will be utilized. If you don’t want to process a specific image, move the georeference data file to another directory before proceeding. Alternatively, you can load individual image files rather than all of the files in a directory Note: If you are using GeoTIFF images with accompanying geodetic reference data files (e.g. TIFF world files) the OrthoVista status window will inform you that there are 2 georeference information. In this case, the TIFF World files (tfw) are overruling the geotiff information. To load input imagery from a directory: Select Load Orthos by Directory from the Setup menu or press the corresponding icon buttons. OrthoVista displays the Find Directory dialog. Select the directory containing the input images and click OK. OrthoVista loads the imagery into the main window and displays the boundaries of each individual input file in red. To load input imagery by file: Page 33
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Select Load Orthos by File from the Setup menu or press the corresponding icon button. Select either tfw, ads or tif (in case of geotiff images) files. OrthoVista displays the Specify Input Files dialog. Select the input image(s) and click OK. You can load each image individually or select multiple images. If you select multiple images, OrthoVista checks for georeference information (e.g. tfw files) and loads only these files. Once you’ve loaded your input imagery, you can modify the display as explained in the previous section. In case of ADS Pushbroom files select the ADS files to load the images. This will then load automatically all files belonging to an ADS file. General Preferences By Selecting the Set General Preferences function the following Global settings window is started.
Figure 11:
General Preferences Dialog
Standard Cache Size This parameter defines a cache size, which is used to cache meta data for computation purposes. Note: Beside the given Cache Size, OrthoVista needs more memory to process data, especially when “Save Vector Seams” is activated. If too much cache size is defined with larger projects the physical memory will be reached. The operating system will then either kill OrthoVista or the computer uses the virtual memory, which slows down Page 34
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processing considerably. According to our testing, a larger cache size does not necessarily speed up processing but can enhance the reaction time in the Radiometrix Editor or if rgn files keeping Background Pixel information are large. Seam Editor Cache Size This parameter defines a cache size, which is used to cache meta data and images for Seam editing. For 64bit operating systems, the cache size can be set to 1024 when having at least 4GB RAM in the computer Log File This parameter is for problem tracking only. Should you have a problem with the OrthoVista processing then it might be helpful to define a log file and enable the Verbose switch. When done try to reproduce the problem and send the Trimble Geospatial support team the log file. Display Background Color This parameter defines the background color of the OrthoVista main window area. Email Settings OrthoVista allows sending emails once a process has finished. The email address and SMTP settings are defined within the email settings dialog. Enable Parallel Processing OrthoVista allows parallel processing for the generation of region files, the HotSpot Removal, Feature Detection and for writing output images when this option is enabled. When enabled the number of parallel processes can be selected. Maximum number is 16. Do not select more processes then cores are available on your computer. Should you have only one core (CPU) available we suggest to enable this option but to select 1 for the number of sub-processes. Dependent on the file IO speed there might not be much improvement in speed between 2 sub-processes and more. Only by improving the file IO 3 or even 4 sub-processes will allow faster processing. Overview Generation Overviews or a Full Set of Overviews are down sampled (minified) images of the original input image. They are stored in separate Files in the same directory as the input images. They have the file extension .pyr. The overview files are very important for a fast display of the images and for fast processing. Therefore we strongly suggest generating overviews if they do not exist. If the parameter “No Overviews” is activated OrthoVista will not create Overviews. If the parameter “Single Overviews” is activated, then OrthoVista will generate one single Overview per image (if it does not already exists) with an extension of about 1024x1024 pixels. If the parameter “Full Set of Overviews” is activated, then OrthoVista will generate several overviews with a downsampling rate factor of 2 from overview to overview. A full set Page 35
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of overviews allow a much faster zooming into the images, and is especially helpful if you use the images in the Seam Editor. If “Delay Overview Generation” is activated, then OrthoVista computes the Overviews only if they are opened for display or accessed for computation. Otherwise OrthoVista will start the overview generation in a multi-threaded mode as soon the images are loaded. Note: No computation of overviews for an image is done if either one or several overviews already exist. Enable Background Checking To enable automatic detection of background pixels, click on the Enable Background Checking checkbox. If your images have no background pixels you can disable this parameter. If disabled all pixels will be treated as valid image data, and the processing is faster. Minimum Non-Background Image Data Value Maximum Non Background Image Data Value To set the pixel values that will be considered background, change the minimum and maximum values in the Image Data Values box. If your images have black borders, set a range from 1 to 255 for 8 bit and 1 to 65535 for 12/16 bit images. If they have white borders, set a range from 0 to 254 for 8 bit and 0 to 65534 for 12/16 bit images. If you do not have black or white borders, disable Background Checking. You can define the Min/Max values independent on the input or output image resolution (8, 12 or 16 bit). The 16bit options give higher resolution steps. Note: If you define the Min/Max range from 1 to 254, you are defining both black and white as background information. In this case OrthoVista tries to fill such background colors with valid image data from overlaying images. If such areas cannot be filled from overlaying images, OrthoVista uses the parameter Output Background Color to fill the areas. It is possible that a white area is transformed to black or vice versa. Output Background Color This parameter defines the color to be used to fill Background Color areas if the areas can’t be filled by valid image data. Display Mapping To control which image data are displayed in a specific display channel, change the values in the Display Mapping boxes. See also chapter 3.9.2. Note: Changing the settings for Min/Max Image data values and Background Checking invalidates all meta data files generated with the previous settings: This includes: *.rdx Radiometrix data files *.rgn Boundary Region files Page 36
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*.bal Image Balancing files *.tlt Group Adjustment files *.cld Seam Definition files If you apply the changes, you have to delete all previously generated meta data files in the meta data directory and the *.rdx files manually. In addition you have to restart OrthoVista before the changes are effective.
3.9.1 Background pixels Images are considered to have two pixel types consisting of either “image pixels” or “background pixels.” A common situation in which this occurs is when a rotated image is ortho-rectified. For example, if a square image is aligned 45-degrees from North and is rectified into a North-South coordinate system, the resulting data file will consist of a diamond-shaped area of image pixels surrounded by triangular areas of background pixels. Because background areas are commonly produced during ortho-rectification operations, OrthoVista provides several options for handling them. A significant feature of OrthoVista is the ability to automatically detect the border between the background pixels and the image pixels. The distinction between image and background pixels is controlled by the Image Data Values minimum and maximum values. By default, background pixels are defined as pixels, which have an intensity value of 0 (0,0,0 for black) or 255 (255,255,255 for white). These values can be adjusted higher or lower respectively to determine what will be considered background pixels. If the pixel intensity value is greater than or equal to the minimum and is also less than or equal to the maximum, then this pixel is considered to be a valid “image pixel.” If the intensity is outside of this range (and is connected by other background pixels that touch the edge of the data file), the pixel is classified as a “background pixel.” In mosaicking, the pixels will be treated as background if they are outside the edge of the image data. However, in image balancing, all values that are background will be ignored no matter where they are located.
3.9.2 Display mapping OrthoVista allows handling multi-channel images. But a color monitor can display only 3 channels as RGB images. For a multi-channel image it is therefore necessary to define which channel shall be combined to show up as Red, Green and Blue. See also chapter 3.14.2 for a description of the RGB channel assignment. Note that grayscale images are always displayed as grayscale independent of the display mapping settings (e.g., the 0 image channel is displayed equally in the display R, G and B channels). The image channels are denoted by the names Red, Green, Blue and if more channels are available with a number starting with 0. For example, a grayscale image has only channel 0. A typical color image has three channels: Red, Green and Blue. The display has three-color channels: red, green and blue commonly identified as R, G and B, respectively. Page 37
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You can use these setting to view individual image channels. For example, if you want to view only image channel 0 (typically the red channel of a color image) as a grayscale image, you can set all display channels to this same image channel.
3.10 Specifying a custom area If you don’t have a tile definition file, you can use this function to define tiles for processing. To specify a custom area: Click Select Area
Figure 12:
Custom Area dialog
Click in the Tile Id box and type a unique name for the new tile you want to define (e.g., ”area01”). Be sure to use different names for each Tile ID you define. OrthoVista will warn you if you try to use the same Tile ID twice. To define the custom area, do one of the following: Click and drag a rectangle in the main window. Type exact coordinates in the data entry boxes and click the Add Tile button. Click the Select All button. OrthoVista displays the custom area you’ve defined (green shaded). The new tile will be stored in the project as an area to be processed. You can select multiple areas for processing at the same time, just be sure to use different names for each Tile ID. To deselect the area, left-click on the main window while the Custom Area dialog is still open.
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3.11 Selecting one or a group of tiles: After having loaded tiles with Load Tile definition (see chapter 3.7) it is necessary to define which tile shall be processed. This definition is done with the Tile Selection. To select an area of predefined tiles, you can select individual tiles or groups of tiles. Choose Select Tiles.
Figure 13:
Select Tiles dialog.
Select From Layer drop-down box: Choose Tile Borders to define a processing area by clicking on the blue tile borders (assuming you’ve loaded a tile definition file). Choose Ortho Borders to define a processing area by clicking on the red image borders to select all tiles that overlay the image. Selection Mode. In “Tile Borders” mode, you can define the processing area by selecting individual tiles (by their tile or orthophoto borders) or by dragging to select multiple tiles. If you set the Selection Mode to “Single Tile,” simply click each tile in the main window that will become part of the processing area. You can select one or more tiles. If you click on a tile again it will be deselected from the processing area. If you set the Selection Mode to “Select Area”, you can use your mouse to click and drag a selection rectangle around a group of tiles to define the processing area. Dragging a rectangle across tiles that are already selected will deselect them from the processing area.
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Figure 14:
Tile selection
The tile selection display can be turned on or off using the bottom icon found on the left side of the main window. To deselect one or a group of tiles: In “single tile” Selection Mode, click on the specific tile to be deselected. In “select area” Selection Mode, drag through the selected tiles again to deselect them. (Note that when the Select Tiles dialog is open, this operation replaces the zoom operation in the main window.)
3.12 Begin Processing The begin processing button starts the setup window for processing options, and allows starting the process after having defined some of the parameter options. See chapter 0 for a detailed description.
3.13 Clearing the defined processing area This function clears all previously defined processing areas and tile selections. It should be used if you want to restart with new definitions of processing areas or tile selections.
3.14 Image Commander The Image Commander allows to Generate overviews for the images Assign which channels of an image contain the RGB channels View single images Page 40
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The Image Commander is a tool available for all ApplicationsMaster applications and is now also integrated in OrthoVista. The main purpose for OrthoVista is the assignment of the RGB channels.
Figure 15:
Image Commander window
3.14.1 Generation of Overviews Select first the images for which overviews shall be generated and then press the button Generate Overviews.
Figure 16: Generate Overview option dialog Define your options for the overview generation and press then the Start button. Note: The Schedule Task option is at time not supported in OrthoVista. For more detailed information, please refer to the ApplicationsMaster Reference Manual.
3.14.2 RGB Channel Assignment The channel assignment allows you to define if and which channel of your image contains the Red, Green and Blue bands. This assignment allows you later on to address the channel with the names Red, Green and Blue. Select first the images for which you would like to assign the RGB channels and then press the button RGB Channel assignment. Page 41
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Figure 17: RGB Channel Assignment option dialog Define now if your selected images contain RGB information and in which channels they are.
3.14.3 Radiometrix This option allows you to start the Radiometrix Tool. See chapter 3.15 for a detailed description on the tool. The difference here is that the Image Commander lets you select the images for which you would like to use the Radiometrix Tool.
3.14.4 View Image The image viewer allows selecting a certain image and start then the Image Viewer, which is also a standard viewer developed for the ApplicationsMaster environment.
3.15 Radiometrix Editor During normal processing, OrthoVista matches the colors, contrast and intensity from one image to the next throughout the processing areas. If the input images are fairly uniform in color, contrast or intensity, you probably won’t need to use the Radiometrix Editor. However, if some images were flown at different dates or if the film or scanner settings varied for different images (or groups of images), you can use the Radiometrix Editor to make corrections to the selected images. The Radiometrix Editor also can be used to stretch the histogram of 16 bit images that appear dark or almost black. The reason for the dark images is that usually the digital sensors only are able to record 11, 12 or 14 bit, but store the image in a 16 bit format.
3.15.1 Adjusting images with the Radiometrix Editor By starting the Radiometrix Editor the first time OrthoVista computes for all images the min/max and mean values in color/intensity/contrast and saturation. These values are then displayed in different tabs.
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Figure 18:
Radiometrix Editor
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Shortcuts The following shortcuts are available to activate specific functionalities for further usage. Shortcut S U M z Arrow Keys
Function Select Images Unselect Images Activate Modify Activate Zoom Move point in curve correction
Zoom in/out Can be done by pointing with the cursor on a position and pressing the “+” or “-“ keys on the keyboard. If zoom is selected zooming can be also done by dragging a rectangle with the left mouse button. Pressing the right mouse button zooms to the previous zoom level.
Selecting/Unselecting images The Selection/Unselection of images can be done either in the project dialog or in the main window. Selection/Unselection in the Project Dialog is done by selecting first images of the image list and pressing then the select or unselect buttons. Selection/Unselection in the Main Window is done by pressing the Select/Unselect button in the Radiometrix Editor and then clicking with the left mouse button on an image or by dragging a rectangle. All images can be selected or unselected by pressing in the Radiometrix Editor the Select All or Unselect All buttons.
Color Space The color space shows the average color of each individual image. The red dot in the center of the color editor represents the center of the color space (perfect gray).
Intensity/Contrast Space The intensity/contrast space shows the average intensity and contrast of each individual image. The intensity changes from left to right (dark to bright) and contrast changes from top to bottom (low contrast to high contrast). The red line represents the mean intensity.
Saturation Space The saturation of the images is displayed in the so-called YUV color model. In the YUV color model the color is decomposed into three components called Y - luminance U - Cb: Chroma channel, U axis, blue component V – Cr: Chroma channel, V axis, red component The range of the U and V values is from –0.5 to +0.5 U = V = 0.0 is gray, +/- 0.5 are the extreme color values.
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Each dot represents the average of the U/V values of an image. The red line represents the centerline of the UV range. To make adjustments, you should zoom into the dot display area since very small changes have a large impact on the saturation which is highly important to image quality. Changing the position of an image along/parallel to the red line, enhances the saturation for all colors. Moving the dot away or closer to the line changes the saturation for a specific color only. Note: in case a group of images is selected, the center of the image group is represented as a green dot. This can help the user to estimate the manual modification in an easier way.
Selective Color Correction The Selective Color Correction function allows changing particular colors in images without affecting others. This is done using the HSL color space. (H=Hue, S=Saturation, L=Lightness). The reset button resets the values to default. Hue: Hue describes the individual values on the chromatic circle
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It can be modified for the reds, oranges, yellows, greens, aquas, blues, purples and magentas of a color.
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Figure 19:
Default settings Hue
Figure 20: Modified settings for purples – The blue has changed in the swimming pool Saturation: Saturation is the colorfulness and is being described in Percent in a range from -100 to +100. The default value is 0 Percent. Saturated, pure color = +100% Medium saturated color = 0% Neutral gray = -100%
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Figure 1: Default settings Saturation
Figure 2: Modified settings for Reds – The car is now having the maximum saturation of red component Lightness: Lightness describes the amplitude of light or the intensity of the color impression. The maximum value would be represented as white, the minimum value as pure black. Full lightness = +100 Neutral gray = 0% No lightness = -100%
Automatic Gradation and Intensity correction This function automatically manipulates the histogram of images, basically to enhance brightness and color. To do this, the histograms of the images are analyzed and the brightest and darkest values are determined. Then the brightest value is defined as white and the darkest as black, and all the other values are proportionally spread. The automatic correction helps to get good results if the full image color range is using the complete histogram, e.g. a 12 bit image stored in a 16 bit file or if the image has a color cast. However the interactive correction can be more precise. To use the function select first the images to modify (See further information below). Then press the “Run Auto-Adjustment” button. The Automatic Gradation correction is preferred for RGB images, as also slight color casts can be corrected. The Automatic Intensity correction is preferred for IR (infrared) imagery, as here, color changes are not wanted.
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Channels: Common Adjustment Based On All Channels Analyzes the histogram of each color band individually. The darkest value of the color bands altogether and the brightest value of the color bans altogether is used as a reference to create a histogram of the “mixed channel”. The amount of stretching for the “mixed channel” is proportionally applied to the individual color channels. Therefore, the automatic manipulation based on all channels should not result in a color cast. Individual Adjustment for Each Channel Each histogram is stretched individually not considering the other bands. Therefore, this automatic manipulation usually will also change the color which in most cases is not wanted.
Images Note that the adjustments are only affecting selected images. However, different options are available to complete the necessary histogram manipulations. Common Adjustment Based On All Images Analyzes the histograms of all images no matter, if selected or not. This option might be used to adapt few selected images to the rest of the block. Common Adjustment Based On Selected Images Analyzes the histograms of the selected images only. This option might be useful if by nature the selected images have a different color or intensity compared to the rest of the block, e.g. water images. Individual Adjustment for Each Channel Performs a histogram manipulation for each image separately without considering all other images. This option might produce a block of images that are looking very inhomogeneous.
Magnitude of Correction: According to the settings for all images or all selected images the software computes the min/max values of the image histogram. The auto-adjustment modifies the histograms of the images by considering the magnitude of correction.
Figure 3:
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Figure 4:
Correction with 100% magnitude
In this case, the histogram is stretched using the full extents of the color range (0256 respectively 0-65535).
Figure 5:
Correction with 90% magnitude
In this case, the difference between the min/max values of the histogram to the maximum extents is computed and the histogram is stretched to 90% of the missing data range. Note: The gradation and intensity correction overwrites enhancements made with the contrast/intensity, saturation and color editor. As a general rule: If you intend to work with all functions of the Radiometrix Editor, always work through the tabs from left to right.
Cutoff Percentage
This option allows to cutoff a certain percentage of the dark and bright pixels of the histograms before they are stretched. The option helps to automatically enhance the images much better as there might be noise on the dark and bright side of the histogram that might badly influence the histogram and therewith the images. Note: Do not cutoff too much as you might lose image content.
Interactive Gradation Curve and Intensity correction This function allows modifying the gradation curves or intensity of only selected images. The changes can be made on individual channels or on the mix channel. Gradation curves are the most flexible tool for image enhancements. The advantage is, that the darkest and brightest image values are not changed (compared to stretching a histogram too much), so that no texture is lost.
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--> X The x-axis of the diagram represents the input of the pixels. The y-axis represents the output values. The dark values (0) are on the left. The linear line represents identical input and output values. To change the color balance/intensity, first select the images you want to modify (See Modifying Images below). Then select the channel you want to modify and activate the Auto Preview button to see the changes in the main window immediately. To change values, click on the curve with the left mouse button. Keep the mouse button pressed and release the button on the desired position. Doing this allows to add as many points as necessary. Each point represents a vertex of a polygon. The resulting modified curve is a B-spline.
To modify vertex points, click on the point with the left mouse button and drag the point by keeping the mouse button pressed. To delete vertex points, click with the right mouse button on the point to delete. The Apply button saves all changes in the corresponding “rdx” files of the images and the curve is then changed back to a straight line. Note: The gradation and intensity correction overwrites enhancements made with the contrast/intensity, saturation and color editor. As a general rule: If you intend to work with all functions of the Radiometrix Editor, always work through the tabs from left to right.
Macro recording: The macro functionality allows recording a set of changes that can be reproducible applied to selected images. The macro has to be recorded on a selection of images, whereas the tabs need to be used from the left to the right side. The macro recording and application is especially helpful when working with large data sets. Therefore please select a subset of representative images for the recording of the macro and apply it afterwards to additional images. Please note that not all Page 50
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functions are supported during the macro recording. These functions will be deactivated as soon as the recording is started.
Record Macro This starts the recording of the macro. The recording can only be started if one or several images are being selected. Changing the selection during the recording is not possible. Stop/Undo Preview Stops the macro after the recording and resets the changes that were applied to the images to their initial state. Stop/Apply Preview Stops and directly applies the recorded changes to the selected images. This option can be used if all images that should be corrected are already selected. Save Macro Saves the macro to a text file (*.rdm). It includes all changes in text format and should not be edited! The file name is suggested based on the recorded Radiometrix Editor functionalities: aG = automatic gradation mG = manual gradation aI = automatic intensity mI = manual Intensity IC = Intensity/Contrast Sat = Saturation UV = Color RSC = Selective Color Correction Load Macro Loads a previously stored macro for further usage on selected images. Apply Macro Applies the loaded or recorded macro to a selection of images. Page 51
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Examples:
Figure 6: Situation before working with the gradation correction
Figure 7: Correcting all channels – images are too bright
Figure 8: Correcting all channels – images are now darker
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Figure 9: Correcting all channels – images are now darker and have more contrast
Figure 10: Correcting upper row of images and blue channel only – too blue images are better adjusted to the other images
Modifying contrast/brightness/color/saturation of images These editors are more intuitive to use than editing gradation curves however, be aware that gradation curves are more flexible to use. To modify images: Select images to be changed. The corresponding dots in the Radiometrix Editor will be highlighted and the center coordinates of the selected images are displayed with Selection Location. Select Modify Click with the left mouse button on a position in the Radiometrix window. This position will be the new position of the group of selected images and the selected images are respectively changed.
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New location
Figure 11: Situation before and after modification with pointer to new position
Relative Mode shifts the average value for the selected images while preserving the relative relationship (and differences) between them. Absolute Mode moves each selected image to the same position. This will cause all the selected images to have the same average value. This can be desirable in giving the group a consistent look; however, it can also shift images away from “true” relative colors. For example, moving the color space of an image containing a brown field to the same colors of an image of a grove of green trees can cause the brown field to look green.
new position
Original Position of selection
relative modification
new position new position
50 % relative/absolute
absolute modification
Now go to the various Tabs with the mouse, and reposition the desired selected images by selecting the new location with a left mouse button click. The selected images will move to the new location and if the main window is displaying the input orthos, the color or contrast/intensity or saturation of the selected images will be changed. Continue with changing the images until you are satisfied with the enhancements.
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History of Changes The History of Changes lists all functions that were used in one session. By clicking into the list of changes, the functionality with the used settings will be opened and can be changed. The undo and redo buttons allow a step-by-step change of the listed steps.
History of Preview Changes The history of preview changes is only available in the manual gradation and manual intensity option. The single steps used in these two options can be undone step-by-step.
3.15.2 Save/Reject changes of the Radiometrix Editor
By pressing the “Ok” button all changes are saved for further use and the Radiometrix Editor will be terminated. By pressing the “Cancel” button all changes are rejected and the Radiometrix Editor will be terminated. By pressing the Undo Changes button any changes made to images since starting the Radiometrix Editor will be undone. By pressing the Reset to Source button all changes are reset and the original color/intensity/contrast values are recomputed from the source images.
3.15.3 Radiometrix Editor: Background information When starting the Radiometrix Editor for the first time, OrthoVista generates a rdx file for each image, on the directory where the images are stored. This makes it necessary that the protection setting for this directory is write enabled. When the Radiometrix Editor is started afterwards, it reads all changes stored in the rdx files. All changes done with the Radiometrix Editor will be taken into account when processing the images. Note they are even used if you have defined none for Single image and Group image adjustment under Processing Options.
3.16 Color Picker The color picker allows checking the color of a certain pixel or the mean color of a selected area.
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Figure 12: Color Picker Window To pick a color of a pixel or a mean color of an area the Pick Point/ Select Area button must be activated first. Then you have to either select a single pixel by clicking with the left mouse button or drag a rectangle. The color picker displays the RGB color values of the pixel or the mean value of the selected area. If several images are overlapping each other at the selected position, the software displays the mean value of all overlapping images. Once such a color is available, it can be assigned to the parameter settings “Display Background Color” or “Output Background Color” or “Reflections Removal Base Color” with the Use as button. If the images are changed with the Radiometrix tool the color picker will immediately change the color according to the changes triggered by the Radiometrix Tool. Multiple Color Picker instances can be active at a time. Each Color Picker indicates its position by a small circle (for points) or a rectangle (for areas).
3.17 Status Dialog The Status Dialog informs about the current status of the processing but also contains information about start and termination of a process. In addition it displays warnings, errors and messages. The status dialog is automatically opened as soon as OrthoVista writes information into the status dialog.
3.18 “Move To…” Dialog This dialog allows moving the display centre to an arbitrary position given by its X and Y coordinate.
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4
Processing Options Once your imagery is loaded and the processing area is defined, you can process imagery using OrthoVista. Almost all image-processing options are controlled in the Processing Options dialog. To begin processing: Select Begin Processing
Figure 13: Processing Options dialog The Processing Options dialog maintains and displays the settings from your last processing run, so you only need to decide which settings to change from your previous session. However, the Output Directory location is not saved. The output directory has to be defined with each start of the Processing Option Dialog. To start processing, click the Close And Process button. OrthoVista processes the images defined by Tile definition or Area definition. A status window shows the status of the processing. When the processing is complete, a small dialog window notifies you that your output images are available. The processing options you specify are automatically saved for the next processing run. The Close button closes the window without processing but saves the current settings. Page 57
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The Cancel button closes the window without processing and without saving the current settings.
4.1 Output options 4.1.1 Specifying the Output Directory The Output Directory is the directory into which the adjusted imagery and/or new mosaics will be written. To specify the output directory either: Click in the Output Directory box and type the appropriate path for the directory. Click the Browse button and use the Select Directory dialog to browse for the desired output directory. Remember to specify an Output Directory location different from the input image directory location.
4.1.2 Meta Data Directory OrthoVista generates the following meta data files. .rgn (region) files contain information about valid image areas. Valid image areas are those areas that do not include background color information .rrn (rotated region) files contain the same information like the .rgn files, but for rotated imagery. .tlt (global tilting) files contain information generated by the global tilting adjustment .bal or .spb (single image balancing) files contain information generated by the single image adjustment cld and fda files contain the seam lines and blending information for the Feature Detection mode cld and agd files contain the seam lines and blending information for the Adaptive Feathering mode autoseam.trn files contains additional blending information for Adaptive Feathering Other interim files are generated during the processing and after a normal stop of OrthoVista automatically removed. These files are interim files that are not important for later processing. The definition of the Meta Data directory is no longer optional. If not defined, OrthoVista computes the above-mentioned data and stores it on the same directory, as the input files are located. By default OrthoVista defines a meta data directory called “meta” which is located on the output directory. The purpose of the Meta Data directory is: Speed up processing. Data is computed then stored and used later when needed again. For instance, the region (rgn) information is needed in OrthoVista and „Seam Editor“. If you run OrthoVista before using „Seam Editor“ and store the meta data, „Seam Editor“ has not to re-compute the information and therefore the project setup is much faster. Transferring balancing and tilting information from one sub-block to another. For instance if you have to process a large block in two separate parts it is helpful to process the first part and store the meta data. Then to process the second part later on with overlapping images to the first part and use the same meta data directory. Meta data, which is already available, is not re-computed but used. With the help of this you transfer then tilting and Page 58
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balancing information from part one to part two. The result is that the radiometric difference between the two parts would be lower as compared to running the two parts independent from each other. Note: Do not use the same Meta Data directory if you just want to re-run OrthoVista with different parameters, as OrthoVista does not re-compute the information if it exists, resulting in no difference between the different runs.
4.1.3 Output Image format OrthoVista supports a variety of image formats. TIFF, BigTIFF and BIP/BIL/BSQ are standard, but other formats may be supported through the use of plugins. To find out the specific image formats supported by your installation of OrthoVista, select About Plugins from the Info menu and select Image Support Plugins. To specify the image file format for the output images, select the desired format from the Image Format drop-down box. Each image format also has a variety of options that can be accessed by clicking the Options button next to the Image Format drop-down box. Note: When changing the image format, the extension for the output filenames will be changed according to the format to reduce confusion and incompatibility with other image programs. Modifying software configuration options may overwrite the specific extension for each file type. For the TIFF and BigTIFF format, additional options may be specified from the TIFF/BigTIFF Options dialog.
Figure 14: TIFF and BigTIFF Options dialogs. Options for TIFF/BigTIFF image format: Layout: Supports Tiled TIFF/BigTIFF and Scanline TIFF/BigTIFF. Sample Format: Supports a variety of Tiff formats.
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Overview: When checked, OrthoVista includes one down-sampled image overview or a full set of down-sampled images as supported by the TIFF format. The Overviews are stored either in a separate file or within the output file itself. The separate files will be located on the same directory as the output files. The overviews, especially a full set of overviews make the display faster for software that supports this TIFF capability. For the BIP/BIL/BSQ format, additional options may be specified from the Options dialog.
Figure 15: BIP/BIL/BSQ Options dialog. Layout: Supports band interleaved by pixel or line or sequential.
4.1.4 Output Report format To specify the georeference file format for the output reports, select the desired format from the Report Format drop-down box. Some report formats have a variety of options that can be accessed by clicking the Options button next to the Report Format drop-down box. GeoTIFF Note: OrthoVista handles GeoTIFF files that contain the image and header data in the same file and supports the following tags in GeoTIFF format: ModelTiepointTag ModelPixelScaleTag ModelTransformationTag Other tags that describe projections as well as extensions that are not supported will be carried through the process and written in the output files without alteration. More information concerning GeoTIFF can be obtained from OrthoVista’s Info menu. The fractional precision and notation of coordinates stored in the TiffWorld file can be changed with optional parameters.
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Figure 16: TiffWorld file format options The notation style options are Fractional which generates coordinates with a notation like 12.123456 Exponential which generates coordinates with a notation like 0.12123456e4 Automatic generates dependent on the coordinates either the fractional or exponential format
4.1.5 Save Background Information for Output Images If this option is activated, OrthoVista automatically generates the region files (rgn files) for the output images. This greatly reduces the time for activating the images in the Seam Editor, if and only if you load in the Seam Editor your output images. What you only do when you use the Save Adjusted Images option and you load the adjusted images in the Seam Editor or when you do the mosaic file editing in the Seam Editor. In most cases you don’t need this function.
4.2 Adjustment options OrthoVista supports for some of the adjustment options parallel processing. Automatically depending on the used hardware the parallel processing will be activated and up to 8 processes can run in parallel. At time the parallel processing is supported by the region generation, the Hot Spot Removal and the Feature Detection. Please find speed tests about the processing time in the Release Notes.
4.2.1 Specifying radiometric adjustments for single images The following radiometric adjustment methods are available for processing individual images and are described in detail in the following paragraphs: None Hot Spot Removal Intensity Dodging Hint: From experience with many data sets we can say that Hot Spot removal and Intensity Dodging should be only applied when your images show lens vignetting effects or color variances. If either Hot Spot removal or Intensity Dodging has to be applied, the Hot Spot Removal function works better for color images and the Intensity Dodging function better for black and white images.
NONE If you select None, single image processing will not be performed on individual images. This is the default and should be selected whenever possible.
Hot Spot removal Applies correction to compensate for effects such as illumination “hot spots” and lens vignetting. See also chapter 5.5. Corrections are applied to each input image individually. For hot spot removal, additional options may be specified from the Hot Spot Removal dialog.
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Figure 17: Hot Spot Removal dialog. Hot spot removal Options: Images with large Background Areas Should be activated if the images have many pixels with background color. If this option is not activated but the images have large background areas, the relevant images will be skipped for Hot Spot Removal Sampling Grid Size. The number in this box defines the number of samples taken in each of two directions from each of the input images to derive the optimal balancing parameters for each image. The grid size value affects the quality of the balancing correction in the output image. Larger values produce better quality but require more processing time. The data range is 40-300 if “images with large background areas” is deactivated and 50-2000 if “images with large background areas” is activated. Note: At least 1500 valid samples are required for the Hot Spot Removal Example: An image is covered with about 20% valid image pixels (80% background color). 1500 samples need to cover 20% of the image 1500 samples = 20% 7500 samples = 100% Sqrt(7500) = ~87 => 100 To make sure enough samples can be derived, a sampling grid size of 100 should be defined. Method. The “method” defines the algorithm used to perform the radiometric corrections. Often, one method is better than the other for certain types of projects. Additive is generally much faster than Multiplicative (see the ”Additive vs. Multiplicative” section in Chapter 6 “Advanced Techniques”). Maintain Intensity. The Maintain Average Input Intensity checkbox defines whether the software will ensure that the average intensity of the output images after radiometric Page 62
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correction will match the average intensity of the input images. Average Intensity “on” best preserves input image intensity. Apply Color Correction (For Color Images Only). When enabled, individual image processing includes correction for systematic color trends within individual images. If disabled, color remains unaffected and only the intensity is modified during processing.
Intensity Dodging Performs intensity modification to remove complex intensity variation within images. Corrections are applied to each input image individually. See also chapter 5.6. For Intensity Dodging, additional options may be specified from the Dodging options dialog.
Figure 18: Dodging options dialog Intensity dodging options: Grid size and Sample Size. Together the two "Sampling Grid" options work as follows. Assume only one dimension (e.g. across a row) for illustration - but the algorithm works in two dimensions. For illustration, assume a (very) small image with 36 by 36 pixels. If GridSize=4, this image will be sampled at 4 equally spaced locations in each direction. At each location, many of pixels are sampled. SampleSize determines the number of pixels sampled at each location. E.g. if SampleSize=3, then three adjacent input image pixels will be used in the computation. Of course the sampling is done in each of 2 dimensions, so that a SampleSize=3 actually includes 9 pixels in the computation at each of the 16 (4x4) locations. So for this example, there are a total of 1296 pixels of which 144 pixels (3x3 x 4x4) are used in the computation. This example is illustrated graphically in the following: The "+" indicates the location on which each sample is centered (remember this will actually be done in each dimension - so that for a 36x36 pixel image, a grid of 4x4 locations will be selected. ----+--------+--------+--------+---At each location, a sample of contiguous pixels is taken. Below, the "X" indicates pixels used in the computation. In two dimensions, a patch (e.g. 3x3 Page 63
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for this example) is sampled. ---XXX------XXX------XXX------XXX--If the SampleSize parameter is 0 or negative (e.g.
