image pre-processing

This section describes a few of the different pre-processing tools available for historical scanned images, which are broken into two categories:

• geometric tools, for re-sampling images so that they have the same shape. This makes it easier to estimate the intrinsic camera parameters (e.g., principal point, radial distortion, affine/decentric parameters).

• radiometric tools, which include steps such as de-striping, contrast enhancement, and de-noising scanned images. These steps can improve the end result, as well as the performance of the matching algorithm(s) used to extract elevation.