Based on bistatic

squint and spatial baseline characteristics of spaceborne parasitical interferometric synthetic aperture radar（InSAR）

models of absolute and relative digital elevation model（DEM） errors are set up.The influence of baseline decorrelation imposing on interferometric phase error is analyzed in detail

which is an important influence of DEM error.The absolute and relative DEM performance of interferometric Cartwheel and Pendulum are simulated.The relation of absolute and relative DEM accuracy with baseline vector are simulated too.Two classical approximate geometries including side-glance and identical range-elevation plane geometries are analyzed.The absolute and relative DEM accuracy of them are compared with those of actual geometry.The simulation results show that baseline decorrelation must be considered in DEM accuracy analysis of spaceborne parasitical InSAR

relative DEM accuracy value is prior to absolute DEM accuracy value

the classical approximate geometry bring great errors which cannot be neglected.