Terrain-Considerate Registration Method of spaceborne LiDAR with InSAR DEM

Objectives: The fusion of spaceborne Light Detection And Ranging(LiDAR) and InSAR(Interferometric Synthetic Aperture Radar Digital) Digital Elevation model(DEM) is widely used in understory terrain estimation, tree height inversion, DEM accuracy evaluation and correction, etc. However, due to limitations in onboard platforms, imaging technology, and data processing, There exist deviations in plane position and height measurement in the InSAR DEM. Therefore, the effective registration of spaceborne LiDAR and InSAR DEM is the key premise of the fusion application. Methods: An improved registration model that fully considers the changes in plane offset and elevation variation under different topographic factors has been proposed, which includes a stochastic model and a functional model. The stochastic model is proposed based on the relationship between changes in terrain slope and plane offset, while the functional model linearizes the original registration model. Finally, The plane offset can be solved using the registration model through least squares adjustment method. In order to verify the validity of the registration method, four test areas with different terrain conditions and land cover types in Spain were selected for testing. Results: The experimental results showed that the RMSE of height difference in the four test areas reached 0.931m, 1.381m, 1.034m and 4.526m respectively after registration, and the accuracy was improved by 33.02%, 8.78%, 37.67% and 10.00% compared with that before registration. Among them, the contribution of slope greater than 45° to the overall registration of elevation changes in the 4 study areas reached 72% to 99%, while the registration accuracy decreases from 33.02%, 8.78%, 37.67%, 10.00% to 20.60%, 0.27%, 35.89%, 4.62% respectively for a canopy height of 15m compared to 5m. Conclusions: This method weakens the systematic error variation of height deviation caused by plane offset under the influence of terrain slope and aspect. The experimental results have verified the effectiveness of the model proposed in this paper for the registration of spaceborne LiDAR and InSAR DEM in complex terrains.