In the third term R/(H - Ah), because His much greater than
Ah, the value of the term decreases rapidly from aerial photography
to satellite imaging. Note that the satellite image
covers a much larger ground area. In its nadir area, the distance
from the nadir point to the object, R, is small, and,
therefore, the corresponding terrain relief displacement will
be small; in the most imaged area, R is sufficiently large in
comparison to Hand a ratio of RI(H - Ah) becomes close to
that of aerial photography.