Geocentric distance´s errors´ correction of space cameras based on USGS DEM

In order to correct the geocentric distance´s error of TDI (Time Delay and Integration) CCD space camera in calculation of image motion compensation, and eliminate the influence to the relative error of image motion velocity, a model of image motion calculation of nadir has been introduced, and the influence of the geocentric distance error to the relative error of image motion velocity has been analyzed with the model; the data source of the earth´s height above sea level USGS DEM (United States Geological Survey Digital Elevation Model) has been introduced to make digital elevation map, and correct the error generated by the different heights above sea level. After correcting, the calculation and analysis of the model shows that: the maximum error of image motion velocity about 1.72% has been decreased to 0.06%; the match error of the forward direction (the integral direction of TDI CCD) has been greatly decreased by correcting the geocentric distance error, which greatly improves the imaging quality of TDI CCD space camera.