In this paper, a much more rapid method of raw data generation is applied, starting by simulating the SAR image itself. Conventional methods of translating a thermal IR- or photographic image into a SAR image are first briefly reviewed. The complex numbers representing the SAR image are then converted to radar raw data using the SAR-processing algorithms backwards. The key transform is the scene center focusing, which ties together SAR data and sensor geometry. This method of generating raw data is shown to be several orders of magnitude faster than the direct method described above, and raw data from the I- and Q-channels can readily be simulated even on a PC. The effects of internal noise and phase errors, due to imperfect motion compensation, can also be included and simulated in detail. The method is exemplified, showing the phase error effect on the SAR-image of an urban scene, the use of autofocusing to restore the image resolution, and finally the degradation due to additive noise on the collected SAR raw data.