What is the purposes of radial triangulation?

Answer 1

Photogrammetry radial triangulation is the purpose to make the ground control. Many phase of it are depends upon ground control for suitable results. Radial triangulation based upon lines radiating from the center of each of two overlapping photographs to certain objects appearing on each photograph

Radial triangulation is a traditional graphical technique for extending horizontal control and compiling plan metric maps from aerial photographs. Numerical methods have been used in conjunction with electronic computers to perform this operation. The photogrammetric principle in radial triangulation that relief displacement, radiates from principal point on a truly vertical photographs means that angle measured about that point in plane of the photographs are true horizontal angle regardless of the elevation of point involved.

Radial triangulation consists basically of successive resection and intersection so it is necessary to have photographic overlap greater than 50 per cent. In addition, images of at least two and preferably more horizontal control point must appear somewhere within the assembly of photographs.

All available horizontal control in the project area should be plotted on a map sheet and the radial triangulation fitted to it. This adjustment is difficult with tracing paper templates but conveniently done with slotted templates or metal arm, an important factor when extensive work is scheduled.