Analysis of the InSAR flattening errors and their influence on DEM reconstruction

For interferometric SAR (InSAR) processing, the interferogram flattening is crucial for reconstructing DEM with high accuracy. In this paper, various error sources of the two techniques for flattening, using the orbit data and the interferogram spectrum, are analyzed. Their comparisons and especially the influence on final DEM accuracy are also discussed. Experiment with different sample data are further carried out to validate the theoretical analysis. Results show that the orbit-based flattening algorithm with the precise orbit data will be obviously better than the spectrum-based one; However, coordinative DEM errors will be derived from the orbit-based flattening algorithm, compared with the spectrum-based one, only with coarse orbit data; Although under whatever situation, high DEM errors will be resulted from the spectrum-based algorithm, if the mean spatial interferometric spectrum is more inclined to zero, the DEM reconstruction will be more accurate. All of these can be well in accordance with the theoretical model of DEM errors.