SUG541 - Advanced Photogrammetry - 17 Questions

MARA UNIVERSITY OF TECHNOLOGY BACHELOR OF GEOMATIC AND SURVEYING SCIENCE (AP220) Jack Ruzaini ([email protected]) ADVANCED PHOTOGRAMMETRY (SUG541) ASSIGNMENT 1 _________________________________________________________________________________________________________

QUESTION 1

What is Photo Scale? 1.

Photo scale is the ratio of a distance on the photo to the corresponding distance on the ground.

2.

Photo scale may be presented as unit equivalents, unit fractions, dimensionless representative fractions or dimensionless ratio.

3.

Photo scale is shown as where one unit on the photograph represents a specific number of the same units on the ground. For example, a photo scale of 1 : 15 000 means 1 mm unit on the photo is represents 15 000 mm or 15 metres unit on the ground.

4.

Two common types of photo scale are: i.

Large Scale – means the larger ground features and more detailed in size. However the area of ground coverage on the photo is less than at smaller scales.

ii.

Small Scale – means the smaller ground features and less detailed size. However the area of ground coverage on the photo is greater than at larger scales.

QUESTION 2

List out information that can be obtained from an aerial photograph. 1.

Number of Photo

2.

Flying Height

3.

Time

4.

Date

5.

Scale

6.

Number of Flight Line. Example, L1N means Line One Northing

7.

Film Colour. Example, FC 1220

8.

Focal Length

9.

Type of Camera

10.

Four (4) Fiducial Marks

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MARA UNIVERSITY OF TECHNOLOGY BACHELOR OF GEOMATIC AND SURVEYING SCIENCE (AP220) Jack Ruzain ni ([email protected]) ADVANCED PHOTOGRAMMETRY (SUG541) ASSIGNMENT 1 _________________________________________________________________________________________________________

QUESTION 3

If a distance of a line on the photograph is known as 1 c cm, m, what is it’s equivalent distance on the ground if the photographic scale is 1 : 10 000

Distance of a line on the photograph 1 cm means 10 mm unit Photo Scale 1 : 10 000 means 1 mm unit on the photo represents 10 000 mm or 10 m on the ground.

If the distance on the photograph is known as 10 mm, so the equivalent distance on the ground is 100 000 mm or 100 m on the ground. QUESTION 4

How many fiducial marks you can see on an aerial photograph? Categorize them. There are four (4) or eight (8) fiducial marks on an aerial photograph. And it falls into few categories: 1.

Circle

2.

Square

3.

Rectangle

4.

Diamond, etc

QUESTION 5

Define what is principal point. 1.

Principal rincipal point is defined as a point that lie on the focal plane and the geometric centre of photograph.

2.

It is also the intersection point between lines that link the opposite fiducial marks marks.

3.

It is also the nadir of the optical axis of the camera during the instant of exposure.

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MARA UNIVERSITY OF TECHNOLOGY BACHELOR OF GEOMATIC AND SURVEYING SCIENCE (AP220) Jack Ruzaini ([email protected]) ADVANCED PHOTOGRAMMETRY (SUG541) ASSIGNMENT 1 _________________________________________________________________________________________________________

QUESTION 6

What is the difference between principal distance and focal length of a camera? 1.

Principal distance is the distance between two principal points and it is conjugate.

2.

In theory the principal distance is seems same as the focal length. However principal distance differs from focal length when the lens is focused at a closer distance, the principal distance changes.

3.

Instead the term used in the lab is “principal distance” but when in the field it is called “focal length”.

QUESTION 7

What is fiducial center? How it is determined?

Fiducial Center is the intersection of the diagonal lines connecting fiducial marks, which lie diametrically apart. Fiducial center also the origin of the coordinate x and y given in rectangular.

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MARA UNIVERSITY OF TECHNOLOGY BACHELOR OF GEOMATIC AND SURVEYING SCIENCE (AP220) Jack Ruzaini ([email protected]) ADVANCED PHOTOGRAMMETRY (SUG541) ASSIGNMENT 1 _________________________________________________________________________________________________________

QUESTION 8

What are the differences between a metric camera and a non – metric camera? Metric Camera

Non – Metric Camera

1. Been specifically designed for photogrammetric

1. An unstable interior orientation. The effective

purposes

and

take

large

format

focal length may change for each exposure

photogrammetric images on stable-base film or

and the direction of the optical axis may alter

glass plates

with focusing movements

2. A stable interior orientation, that is lens cone is rigid and the focusing distance pre-set at the

2. A lack of fiducial marks 3. Irregular lens distortions. As well as radial lens

factory. The optical axis is defined by fiducial

distortions,

marks

distortions may be present in the lenses of

fixed

to

the

camera

which

are

reproduced on each exposure as reference points;

relatively

large

tangential

older amateur camera. 4. An unsophisticated film flattening device. The

3. A low distortion lens whose characteristics

film may be buckled at the time of exposure,

(focal length, radial lens distortions) are known

but will be held flat whilst image coordinates

from a manufacturer’s calibration test

are read from it. the buckling may vary from

4. An image surface which is flat within a fine tolerance

and

which

incorporates

a

film

flattening device such as a pressure plate or vacuum system.

frame to frame and consequently is very difficult to correct during calculations for object coordinates 5. Small

image

format.

The

accuracy

of

determining the position of an object by photogrammetry is claimed to be directly related to the area of the photographed image. 6. However the modern lenses available for small format non-metric cameras often have a better pictorial quality than the low distortion and lower resolution lenses in metric cameras.

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MARA UNIVERSITY OF TECHNOLOGY BACHELOR OF GEOMATIC AND SURVEYING SCIENCE (AP220) Jack Ruzaini ([email protected]) ADVANCED PHOTOGRAMMETRY (SUG541) ASSIGNMENT 1 _________________________________________________________________________________________________________

QUESTION 9

Explain the Newton’s Lens Law. Show the expression. 1.

Lens formula: The relation between u, v and f is called lens formula. 1/f = 1/v – 1/u

2.

Lens maker formula: The relation focal length (f), refractive index (µ), radius of curvature of first and second (R1 & R2) which refracting surfaces of a thin lens is known as lens maker formula. 1/f = (µ – 1) (1/R1 – 1/R2)

3.

Newton Formula: Newton’s formula measures the distance of object (x1) and (x2) from the first and second principal foci not from the optical centre. then Newton's formula states f2 = x1x

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MARA UNIVERSITY OF TECHNOLOGY BACHELOR OF GEOMATIC AND SURVEYING SCIENCE (AP220) Jack Ruzaini ([email protected]) ADVANCED PHOTOGRAMMETRY (SUG541) ASSIGNMENT 1 _________________________________________________________________________________________________________

QUESTION 10

What is the differences between an oblique photograph and a panoramic photograph? Oblique Photograph

Panoramic Photograph

An oblique photograph is taken when the camera is

Panoramic photography is achieved by stitching a

focused at any angle between three degrees from

number of photographs together to form a single

vertical and the horizon.

"Wide" shot.

There are two basic types of oblique photograph:

Panoramic aerial photography can be done using

high-angle and low-angle. In high-angle oblique,

full-sized helicopters, their unmanned counterparts,

the apparent horizon is shown, while in low-angle

or pole cams.

oblique the horizon is not. Pole cams are good for very low altitudes but they With high oblique photograph, atmospheric haze

are limited to about 100 feet and road access is

and clouds often prevent the viewer from seeing

needed.

the true horizon. Full-sized helicopters are the platform of choice for The furthest point viewable in high oblique aerial

high-altitude

panoramas;

however

new

photography is called the apparent horizon.

technologies permit unmanned helicopters, coupled with advanced GPS autopilot stabilization systems, to be positioned within a few feet from any elevation or location.

This type of aerial photography is perfect for showing

views

from

proposed

or

under-

construction high-rise buildings. _________________________________________________________________________________________________________ Page 6 of 11

MARA UNIVERSITY OF TECHNOLOGY BACHELOR OF GEOMATIC AND SURVEYING SCIENCE (AP220) Jack Ruzaini ([email protected]) ADVANCED PHOTOGRAMMETRY (SUG541) ASSIGNMENT 1 _________________________________________________________________________________________________________

QUESTION 11

Show the equations of a photo scale for a vertical photo and an oblique photo.

Vertical Photograph

Oblique / Tilted Photograph

1. Scale of Vertical Photograph Over Flat Terrain S=


  
    

2. Scale of Vertical Photograph over Variable Terrain (at a point) S=


     

 S=

H = Flying Height, h = the elevation at point 3. Scale of Vertical Photograph by other method S=

    

!"#$

%& #'($ )*

f = focal length x map scale

y’ = calculated coordinate of the point in the auxiliary system H = Flying height above datum for the photo h’ = elevation of certain object point above datum

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MARA UNIVERSITY OF TECHNOLOGY BACHELOR OF GEOMATIC AND SURVEYING SCIENCE (AP220) Jack Ruzaini ([email protected]) ADVANCED PHOTOGRAMMETRY (SUG541) ASSIGNMENT 1 _________________________________________________________________________________________________________

QUESTION 12

Define the followings: i.

Nadir Point it is the point where a plumb line dropped from the front nodal point pierces the photograph. This point is vertically beneath the exposure station.

ii.

Pass Point

iii.

Tie Point

iv.

Control Point A reference point precisely located on both the ground and the photo (ground control point) on both a map and the photo (map control point), or on two adjacent photos (photo control point)

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MARA UNIVERSITY OF TECHNOLOGY BACHELOR OF GEOMATIC AND SURVEYING SCIENCE (AP220) Jack Ruzaini ([email protected]) ADVANCED PHOTOGRAMMETRY (SUG541) ASSIGNMENT 1 _________________________________________________________________________________________________________

QUESTION 13

What is Snell’s Law? Snell's law (also known as the law of refraction) named after Dutch mathematician Willebrord Snellius, one of its discoverers, is a formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media, such as water and glass.

The law says that the ratio of the sines of the angles of incidence and of refraction is a constant that depends on the media.

In optics, the law is used in ray tracing to compute the angles of incidence or refraction, and in experimental optics and gemology to find the refractive index of a material.

Refraction of light at the interface between two media of different refractive indices, with n2 > n1. Since the velocity is lower in the second medium (v2 < v1), the angle of refraction θ2 is less than the angle of incidence θ1; that is, the ray in the higher-index medium is closer to the normal.

Snell's law is also satisfied in the metamaterials which allow light to be bent "backward" at a negative index, with a negative angle of refraction.

Snell's law states that the ratio of the sines of the angles of incidence and refraction is equivalent to the ratio of velocities in the two media, or equivalent to the opposite ratio of the indices of refraction:

v = velocity, SI units are m/s n = refractive index, which is unitless

Snell's law follows from Fermat's principle of least time, which in turn follows from the propagation of light as waves.

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MARA UNIVERSITY OF TECHNOLOGY BACHELOR OF GEOMATIC AND SURVEYING SCIENCE (AP220) Jack Ruzaini ([email protected]) ADVANCED PHOTOGRAMMETRY (SUG541) ASSIGNMENT 1 _________________________________________________________________________________________________________

QUESTION 14

What are the parameters of inner orientation? 1.

Coordinate system.

2.

Principal distance.

3.

Focal length.

4.

Principal point.

5.

Fiducial mark coordinates.

QUESTION 15

What is relative orientation? How it differs from absolute orientation? Absolute orientation includes the identification of ground control features and the measurement of the corresponding image coordinates. Implementations of automatic absolute orientation are rare and work under restricted conditions only. These measurements, in principle, make ground control information as such, and thus also their identification in the images, obsolete. As it stands today, however, at least a small number of control points are still needed to ensure a reliable solution.

In contrast to absolute orientation, relative orientation does not require the recognition of specific features. The conjugate points used only have to be geometrically well distributed in the model area.

Relative orientation is a prerequisite in order to provide users from photogrammetry and other disciplines with parallax-free stereo viewing for photogrammetric date collection, interpretation purposes, and a number of other tasks.

Relative orientation is also the core for any automatic point transfer system. Moreover, the parameters of relative needed

orientation for

are

epipolar

resampling of digital images. Therefore, automatic relative orientation

is

an essential

procedure for the automation of

further

procedures

photogrammetric

in

stereo

processing.

“Relative orientation” is done by selecting correlative photo points: this eliminates model parallax. _________________________________________________________________________________________________________ Page 10 of 11

MARA UNIVERSITY OF TECHNOLOGY BACHELOR OF GEOMATIC AND SURVEYING SCIENCE (AP220) Jack Ruzaini ([email protected]) ADVANCED PHOTOGRAMMETRY (SUG541) ASSIGNMENT 1 _________________________________________________________________________________________________________

QUESTION 16

There are three (3) types of errors in photogrammetry. Discuss. 1.

Gross Errors – mistakes or blunders caused by carelessness or negligence. E.g. point misidentification, transcription error in recording a value, misreading of a scale.

2.

Systematic Errors – is an error in measurement which follows some mathematical or physical law. E.g. shrinkage or expansive of photograph, camera lens distortion, atmospheric refraction.

3.

Random Errors – generally were small but can never be avoided entirely in measurement. E.g. in estimating between least graduation of a scale.

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