The specific image lines of the strips containing
the object are taken at different times. Thus, the intrack
stereo mode has three combinations of stereo pairs,namely F-N (fore-nadir), N-A (nadir-aft), and F-A (fore-aft). Baselines
are then 271km (Quick Bird) and 680km (IKONOS) for F-N
and N-A stereo pairs, and 542km and 1360km, respectively, for
F-A pairs.