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http://www.fgi.fi/osastot/foto/projektit/satellite_eng.htmlSatellite photogrammetry

The high-resolution satellite images can be used in the production of spatial information with medium-scale geometric accuracy and spatial resolution requirements (1-5 m). Thus, they are an option to the small-scale airborne imagery. Significant technical features of the high-resolution satellite images are high spatial resolution of 1 m (PAN), the pushbroom geometry and along-track stereo. The properties of the high-resolution satellites are listed in Table 1.

Table 1. Properties of commercial high-resolution satellites.

SystemQuickbirdOrbview 3 and 4Ikonos

SensorPAN/MSPAN/MSPAN/MS

Sensor modelPushbroomPushbroomPushbroom

Sensor PositionGPSGPSGPS

Altitude600 km470 km680 km

Max tilting angle304545

Pixel size1 m x 1 m/4 m x 4 m1 m x 1 m/4 m x 4 m1 m x 1 m/4 m x 4 m

B/H ratio1.22.02.0

Swath width22 km8 km11 km

Z accuracy0.5 m0.4 m0.4 m

Stereo modeAlong trackAlong trackAlong and across track

Launch date2000 (planned)2000 (planned)1999 (in operation)

Investigations on the satellite photogrammetry began in 1997 at the FGI. The first investigations concerned the rigorous modeling of the pushbroom geometry. A rigorous method for determination of the orientations of satellite images was implemented to the multi-sensor AT software of the FGI. Orbital and attitude models can be utilized in the determination of the orientations due to the smooth movement of the satellite along the orbit. In the software, the Keplerian orbit is approximated by a circular orbit, letting the radius, however, vary with time. The attitude variations are modeled by up to second order polynomials.

JERS/VNIR and SPOT/PAN images have been used in empirical investigations. The accuracy of orientation of single image and satellite image blocks, and the stereoscopic quality have been evaluated. An example of the results is shown in Figure 1. When orbital and attitude observations of the satellite are utilized, a minimum of 2 ground control points (GCPs) is needed. When 4 or more GCPs were used, the orientation accuracy of the SPOT images was better than 0.6 pixels (6 m) and of the JERS images better than 0.4 pixels (about 8 m)

The accuracy of the orientations of SPOT/PAN and JERS/VNIR images (root-mean-square-error at independent checkpoints) as the function of number of GCPs