Abstract
Interferometric synthetic aperture radar (InSAR) is one of the best methods for obtaining digital elevation models (DEMs). However, the problem of the uncertainty of DEM accuracy affected by the perpendicular baseline still persists, which should be as long as possible to ensure the sensitivity of the phase to the height measurement, and as small as possible to ensure a high spatial coherence. Moreover, the baseline configuration design of bistatic SAR system lacks a more detailed model for reference to generate high-precision DEM. Therefore, in this paper, the optimal baseline is modeled to maximize the accuracy of height measurement. First, we analyze the influence of system parameters on the height measurement accuracy, and a propagation model from the parameter estimation error to the elevation error is derived. Then, the phase unwrapping error (PUE) that considers the spatial baseline coherence, terrain slope and phase unwrapping effectiveness is modeled and analyzed after interferometric phase simulation and adaptive unscented Kalman filter phase unwrapping. Combining the relationship between the height error and the PUE, the optimal baseline model is obtained by statistical analysis. Finally, weighted averages are used to calculate the average slope of the complex terrain and the validity and reliability of the proposed optimal baseline model are verified by two examples of complex terrains with uniformly and nonuniformly distributed positive and negative slope angles. Moreover, the optimal baseline ranges of different terrain types are also derived for reference.
Highlights
Interferometric synthetic aperture radar (InSAR) has become one of the most popular methods in recent years for generating digital elevation models (DEMs)
The optimal baseline ranges of different terrain types are given for reference
Compared with the previous model [3,7], it considered the influence of the perpendicular baseline, the terrain slope and the unwrapping effectiveness on the phase unwrapping error (PUE), and a reasonable weighted average algorithm was proposed to calculate the average slope of a complex terrain
Summary
Interferometric synthetic aperture radar (InSAR) has become one of the most popular methods in recent years for generating digital elevation models (DEMs). The accuracy of the InSAR height measurement is mainly influenced by the positioning system of the satellite platform, the slant range from the radar to the target, the baseline length, the baseline inclination, and the interferometric phase Among these factors, the errors caused by the first four factors and the absolute phase offset [3] are systematic, and the interferometric phase error introduced by various decorrelation factors is random [4]. Equation (10) represents the height measurement uncertainty associated with the interferometric phase error, which is mainly caused by the absolute phase offset and several decorrelation factors The former can be corrected by ground control points, while the latter is random and cannot be corrected by the above method. The parameters H, R1, and α are considered known either by the use of precise orbit information or after an adjustment procedure involving ground control points
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