Object Location of Space-borne SAR Imagery Under Lacking Ground Control Points

The slant-range imaging principle of space-borne SAR sensor is discussed,and from the Range-Doppler equations,the direct georeferencing model without ground control points(GCPs) is formulated.In the conditions of the lack of GCPs,the model for adjusting the model parameters,including the track model parameters and image geometric processing parameters,is derived in detail.Direct georeferencing is made on a scene of ENVISAT ASAR imagery of Beijing area,and planimetric accuracy of 170.966 m(±8.7 pixels) is obtained.After using one GCP to adjust some model parameters,the planimetric accuracy is improved by ±54.665 m(±2.8 pixels).The experiment shows that in the condition of the lack of GCPs the positioning accuracy for space-borne SAR imagery can approximate to two ground sampled distance,and will has a good application prospects,especially for the georeferencing of the difficult areas.