Spot-5 are an typical phototopographic satellite: hrg collected image with 2. 5 meter resolution can be used to orthophoto mapping and detail mapping in scale 1:50000 and 25000; through forward and backward vision, hrs can collect the topographic data and dem data for stereomapping in range 600 km_by_ 120 km. Besides of spatial resolution increased to 0. 7 meter, planning spot pleiades-hr have the capability to collect stereo and tri-stereo imagery for large image coverage through lateral vision and forward/backward vision, as well the capability for surveying and mapping along a river, border and coast line. The satellite phototopography is developing which has the new characteristic as following : for satellite phototopography, the instantaneous satellite position on orbit will be a station from which the forward intersection are carried on, so, the position of station should be computed by using satellite geodesy method and with the accuracy topographic control survey required. With high accuracy time and stable velocity, for a temporal period, satellite move along the orbit a step correspondence to spatial resolution. Either lateral vision or forward/backward vision along orbit the visual direction of sensor are determined by attitude angle. Therefore the grouped stellar observation / imu system are important part of satellite phototopographic system. Along with the development of spatial and temporal measurement technology, satellite phototopographic survey could be conducted with only a few control measurements on the ground.
SPOT products differ by pixel size (ground sample distance of 2.5 m, 5 m, 10 m or 20 m) and spectral acquisition mode (black and white or colour).