flexible scheduling, and
easy-to-change configurations. Among the new commercial
high-resolution satellite imaging systems, the EarlyBird system
of Earthwatch, Incorporated has a ground resolution of 3
m in the panchromatic band and captures images frame by
frame. The pushbroom imaging technique with one or more
linear CCD arrays has been adopted by systems with 1 m resolution.
Such a configuration provides a so-called in-track
stereo mode where stereo pairs necessary for deriving the
horizontal and elevation information of objects can be acquired
in quasi real-time or real-time; cross-track stereo requires
additional time to allow the satellite to point to the
same ground area from a neighboring track. Stereo mapping
capabilities of similar airborne imagers and systems mounted
on board the Space Shuttles have been demonstrated (Heipke
et al., 1996; Fraser et al., 1997). There are four advantages of
high-resolution satellites: (1) the highest resolution ever
available to the civilian mapping community; (2) extremely
long camera focal length, for example, ten metres, for capturing
terrain relief information from satellite orbit; (3) fore-, nadir-,
and aft-looking linear CCD arrays supplying in-track
stereo strips and "pointing" capabilities generating crosstrack
stereo strips; and (4) a base-height (sensor baseline vs.
orbit height) ratio of 0.6 and greater that is similar to aerial
photographs. Table 1 gives some selected technical specifications
of the high-resolution commercial satellites, which are
important for three-dimensional mapping applications (Fritz,
1996). If not specified, parameters used in equations and estimations
in the rest of the paper are based on the IKONOS system
[Table 2).
flexible scheduling, andeasy-to-change configurations. Among the new commercialhigh-resolution satellite imaging systems, the EarlyBird systemof Earthwatch, Incorporated has a ground resolution of 3m in the panchromatic band and captures images frame byframe. The pushbroom imaging technique with one or morelinear CCD arrays has been adopted by systems with 1 m resolution.Such a configuration provides a so-called in-trackstereo mode where stereo pairs necessary for deriving thehorizontal and elevation information of objects can be acquiredin quasi real-time or real-time; cross-track stereo requiresadditional time to allow the satellite to point to thesame ground area from a neighboring track. Stereo mappingcapabilities of similar airborne imagers and systems mountedon board the Space Shuttles have been demonstrated (Heipkeet al., 1996; Fraser et al., 1997). There are four advantages ofhigh-resolution satellites: (1) the highest resolution everavailable to the civilian mapping community; (2) extremelylong camera focal length, for example, ten metres, for capturingterrain relief information from satellite orbit; (3) fore-, nadir-,and aft-looking linear CCD arrays supplying in-trackstereo strips and "pointing" capabilities generating crosstrackstereo strips; and (4) a base-height (sensor baseline vs.orbit height) ratio of 0.6 and greater that is similar to aerialphotographs. Table 1 gives some selected technical specificationsof the high-resolution commercial satellites, which areimportant for three-dimensional mapping applications (Fritz,1996). If not specified, parameters used in equations and estimationsin the rest of the paper are based on the IKONOS system[Table 2).
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