topographic surveying survey2 notes of am fillone, dlsu-manila

Topographic Surveying

Survey2 Notes of AM Fillone, DLSU-Manila

Topographic Surveys are used in the determination of the location of man-made and natural features (e.g. roads, buildings, tree, shorelines, etc.) on the earth’s surface.

This also includes the determination of ground elevations which can later be plotted in the form of contours, cross sections, profiles or simply as spot elevations. In engineering and construction work, these are often called preliminary or pre-engineering surveys

For smaller-area, topographic surveys, ground surveys can be accomplished by using, 1.) transit and tape

2.) stadia, or3.) electronic tacheometry


The choice of field methods for topographic surveying is governed by,

1.) the intended use of the map,2.) the area of the tract,3.) the map scale, and4.) the contour interval.

A contour line is a line that joins points of the same elevation on the ground.


These are several ways to produce a survey drawing using the conventional scale and protractor plotting techniques.

One of these is the arithmetic solution and the procedure of this method is as follows:

1.) Obtain the scaled distance, S, between two points 1 and 2 (any appropriate scale can be used).

2) Obtain the difference in elevation, E, between points 1 and 2.

3.) Obtain the difference in elevation, y, between point 1 and the contour line. The elevation of the contour line could also be obtained by basing it from point 2.

4.) The scaled distance, d from point 1 to the contour line can be obtained as

d = (y/E)*S


Characteristics of Contours


6.) Contour lines cannot begin or end on the plan.


7. A contour never splits.

8. A closed contour indicates either a summit or depression. A hachured, closed contour line indicates a depression. Survey2 Notes of AM Fillone, DLSU-Manila

9. As contour lines represent contours of different elevation on the ground, they cannot merge or cross one another on the map, except in cases where there is an overhanging cliff or cave, or bridge abuttments.

10. As contour lines represents level lines, they are perpendicular to the lines of steepest slope. They are perpendicular to ridge and valley lines where they cross such lines.


11. On uniform slopes, the contour lines are spaced uniformly.

12. No two contours can run into one.


13. Contours deflect uphill at valley lines and downhill at ridge line; line crossing are perpendicular: U-shaped for ridge crossings; V-shaped for valley crossings.

Valley

Ridge


Consider the upper left grid, using the - There are two contours that will pass through b/n corners (1) and (2) – th3 30m and 40m contour lines-To locate the 30m contour line,S = 107mmE = 47.2 – 25.6 = 21.6m

y = 47.2 – 30 = 17.2m

d1 = (y/E)*S = (17.2/21.6)*107 = 85.2mm

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30m

S = 107mmd1 = 85.2mm

40m

-To locate the 40m contour line,S = 107mmE = 47.2 – 25.6 = 21.6m

y = 47.2 – 40 = 7.2m

d2 = (y/E)*S = (7.2/21.6)*107 = 35.67mm

d2 = 35.67mm



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• Since the contour interval is 10m, all contour lines should be multiples of 10.

Solution:Since the contour interval = 10m, we have to use contours whose elevations are multiples of 10.


topographic surveying survey2 notes of am fillone, dlsu-manila

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