Question:

What is the difference between Tie Points and Control Points?

Answer:

A tie point corresponds to pixels in two or more different photographs, where these pixels represent the projection of the same physical point in the scene. ContextCapture can automatically generate a large number of automatic tie points during the aerotriangulation process. User tie points can also be entered a priori from a dedicated interface to help aerotriangulation.

 

Control points are optional positioning data used during the aerotriangulation of the block. Adding control points to a block makes it possible to accurately georeference it and avoids long-range metric distortion.