This requirement can be met easily by forming
stereo pairs using F-N and N-A combinations. Elevation error uh
in a DEM is required to be less than 15 m. This requirement can
be met without GCPs. DOQ and DOQQ (Digital Orthophoto Quarter-
Quadrangles) products have a resolution of 2 m to 1 m, respectively.
Elevation errors of a DEM needed to produce DOQ
are required to be less than 7 m.