Survey 5
Triangulation
The aim is to use triangulation to locate unknown points.
Triangulation splits network of control points into system of adjacent triangles. Angles within triangles are measured and one distance is measured. This distance is called base. Then all the distances can be computed and coordinates can be evaluated.
But in such case—there is no—or only a limited check for errors thus also distance of check base is measured. Check base is located on other side of the network.
1, 2—Triangulation; 3—Triangulation strengthened by more measurements
The equipment
Use total station to read horizontal angles and to determine the lengths of bases.
Important notes
- Use a plumb bob to establish setup over the stations.
- Use a plumb bob (at the targets) when you point the telescope toward the stations.
Evaluation
Evaluate the angles and distances from values measured accordingly. If you choose the overdetermined system of triangles (picture 3 from above), then use
- software for geodetic engineers (LISCAD by Leica), which provides module Adjustment (least square adjustment of field data) or
- split the network into two solutions (picture below) and interpolate between them to find the best fit.
Finally transform coordinates of stations into local coordinate system where A = (0,0) and azimuth AD = 90°. That can be done easily in CAD and is going to be useful to compare the results between the teams.
