Survey 4
Contour lines
The aim is to draw contour lines on selected area.
Engineers, architects and building contractors base their construction projects on maps from topographic or land surveys to help design buildings, dams, housing projects, canals, drainage pipes and other structures. Topographic maps from surveys would indicate the best area for building the structures, how much dirt to move and the possible obstacles the project could encounter.
Contour lines are typically drawn over whole topographic map. They depict approximate lines which run through the same level. Contour lines are usually drawn in equidistant vertical distances (eg. each 1 m, every 5 m, every 100 m).
The process of measurements is made a) on points of interests or b) on grid of grid points. The levels of these points are measured by means of differential leveling. From one setup more measurements are taken (rod shots). Because contour lines do not serve to provide a perfect description of terrain, there is no need to establish network of points using high degree of accuracy.
2—Because the terrain is steep the preparations needs some more planning.
The result will be a plan of surveyed area with contour lines drawn.
Important notes
- Mark corners of the area by wooden sticks. From corners, establish a network of 5 × 4 grid points by tape then.
- Vetical distances between the grid points will be found by level instruments and rods.
- Because terrain is steep the preparations needs some more planning to avoid redundant setups.
- Keep the original field books. Attach them to the protocol.
- Follow rules of maintaining the field book.
Recommendations
Since the leveling is conducted under a steep slope, always try to establish each setup as high as possible. This will reduce count of needed setups and will improve survey's performance.
Evaluation
Since we have no benchmark points, you are free to fix the altitude of the starting point according to your judgment.
