Field Work No. 12 Topographic Survey by Squares or Grid Method

ELEMENTARY SURVEYING FIELD MANUAL

FIELD WORK NO. 12 TOPOGRAPHIC SURVEY BY SQUARES OR GRID METHOD CE120-0F / A1

SUBMITTED BY: NAME:

STUDENT NO.:

GROUP NO. 4 DATE OF FIELD WORK: SEPTEMBER 11, 2014 DATE OF SUBMITTION: SEPTEMBER 18, 2014

SUBMITTED TO: PROFESSOR: ENGR. CERVANTES

GRADE

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FIELD WORK NO. 12 TOPOGRAPHIC SURVEY BY SQUARES OR GRID METHOD

FINAL DATA SHEET FIELD WORK 12

TOPOGRAPHIC SURVEY BY SQUARES OR GRID METHOD

DATE: SEPTEMBER 11, 2014 TIME: 10:30AM – 12:00PM WEATHER: SUNNY

STATION OCCUPIED

H

STATION OBSERVED BM1 (+000) H1 (+005) H2 (+010) H3 (+015) H4 (+020) (TP1) H5 (+025) H6 (+030) H7 (+035) (TP2) H8 (+040) H9 (+045) BM2 (+050)

GROUP NO.: 4 LOCATION: BONIFACIO SHRINE PROFESSOR: ENGR. CERVANTES

BS

HI

1.51

301.51

IFS

FS

1.485 1.445 1.405 0.77

301.405

0.875 0.93 1.415

1.34

301.38

1.365 1.405 1.435 1.445

COMPUTATIONS:

H.I. = ELAEVATION + B.S. H.I. = 300 m + 1.51 m H.I. = 301.51 m

ELEVATION = H.I. – F.S. ELEVATION = 301.51 m – 1.485m ELEVATION = 300.025 m

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ELEVATION 300 300.025 300.065 300.105 300.635 300.475 299.99 300.04 299.975 299.945 299.935

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FIELD WORK NO. 12 TOPOGRAPHIC SURVEY BY SQUARES OR GRID METHOD

SKETCH

TOPOGRAPHIC MAP

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FIELD WORK NO. 12 TOPOGRAPHIC SURVEY BY SQUARES OR GRID METHOD

DISCUSSIONS Topography is the shape, configuration, relief, roughness, or three-dimensional characteristics of the earth's surface. Some of the definitions included in this field work are topographic maps and topographic surveys. Topographic maps shows topography together with natural and artificial features such as streams, lakes, buildings, highways, etc. Topographic maps are used by a variety of professions from engineers, architects, foresters, geologists, etc. The most common use of topographic maps is in the planning stages of projects to help design the layout and location of buildings, roads, dams, pipelines, landscapes, fire control routes, trails, etc. While topographic surveys are surveys made to determine the configuration of the earth’s surface and to locate natural and cultural features on it. Topographic maps (produced by the U.S. Geological Survey) are available for a large part of the United States. USGS map scales are usually 1:24000 which means 1 in. = 2000 ft. Additional government agencies may also have topographic maps at various scales that may be suitable for your needs.

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FIELD WORK NO. 12 TOPOGRAPHIC SURVEY BY SQUARES OR GRID METHOD

Topographic surveys are determining the relative locations of points (places) on the earth's surface by measuring horizontal distances, differences in elevation and directions and topos (Gr.): place; topographic maps give the locations of places (observable features); they serve as base maps. Topographic surveys are very useful in geography. Some of the uses of the topographic surveys are producing topographic maps, constructing topographic (cross-sectional) profiles, and establishing vertical and horizontal control for accurately defining locations.

Methods 1. Horizontal distance 

Tachymetry: a rapid optical means of measuring distance using a telescope with cross hairs and a stadia rod (one stadium = about 607 feet).

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FIELD WORK NO. 12 TOPOGRAPHIC SURVEY BY SQUARES OR GRID METHOD



Measuring slopes distance with a tape and reducing it to horizontal distance using the cosine of the slope gradient.

2. Difference in elevation 

Leveling with a level telescope and a stadia rod.



Measuring a vertical angles and a slope distance (height is the product of the distance and sine of the angle). Leveling is more accurate since elevation differences are measured not

calculated. Two readings are taken at each position of the automatic level: a backsight towards a station located before the level on the traverse and a foresight to the next station on the traverse. Thus the stadia rod occupies two stations, before and after the level on the survey. The difference in elevation between successive stations if the difference between the backsight and the foresight read from the stadia rod. For each position of the level, the lengths of the foresights and backsights should be approximately the same since accuracy is a function of the distance of a sighting. The level operator should anticipate the distance to the next station and set up the level midway along this distance (note: the distance that can be sighted decreases with increase in slope, since the stadia rod will disappear above or below the level line of sight). The lengths of backsight and foresight can be paced by the rod person or measured by the interval between the upper and lower cross hairs (tachymetry). 3. Direction 

horizontal angle measured with a compass



precise measuring devices use vernier scales



direction is expressed relative to a reference line or meridian o true meridian: a north-south line o magnetic meridian: a line parallel with the earth's magnetic lines of force o assumed meridian: an arbitrary line

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FIELD WORK NO. 12 TOPOGRAPHIC SURVEY BY SQUARES OR GRID METHOD

CONCLUSION On this field work, we tried to determine the topographic survey of a traverse by squares or grid method. The objectives of this field work are to learn how to perform topographic survey of a hilly terrain, to acquire the knowledge of plotting the different contour lines, and to develop the skills in the identification of the different element in a contour map. According from the lecture being discussed, a traverse must be closed field. The common sources of error on this field work are the inaccurate reading of measurements, human errors and instrumental errors. Human errors include reading the azimuth of a given point even if the bubble of the total station is not yet on the center and not reading the measurements on the tape accurately. Rotating the total station counter clockwise is also one of the common sources of error. While instrumental errors include if the instrument/s used for getting the data in the field work, which is a total station for this field work, is/are defective or out of battery. It is recommended to have patience in doing the field work because this field work has so much part and a lot to be done. Also check first if the measuring tape is completely perpendicular to the ground before recording the measurement to lessen the error that might be acquired. Using a plumb bob is also recommended to see if the measuring tape is perpendicular to the ground. Team work is also required for this experiment because everyone has their assigned task to do to finish the field work on time. Follow the instructions on the manual carefully to avoid errors.

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