A new lunar global DEM derived from chang'E-1 laser altimeter data based on crossover adjustment with local topographic constraint

This paper presents a crossover adjustment method with local topographic constraint and a new lunar global digital elevation model (DEM) derived from Chang’E-1Laser Altimeter (LAM) data based on the crossover adjustment. With about 9.12 million altimetric points acquired by the LAM, we derived more than 141,000 crossovers that cover the entire lunar surface after eliminating outliers of orbits and altimetric points. The global lunar surface is divided into 32 local blocks, and the least squares adjustment of crossover differences is performed for each block using the local topographic constraint information extracted from the planar areas. Smooth transitions among the neighbouring blocks are ensured through sufficient overlapping areas and virtual control points from the planar areas. After the crossover adjustment, root mean square (RMS) of the residuals is reduced from 149.51m to 54.75m after using three parameters for each profile in each block in the mid-latitude region. In polar regions, RMS is reduced from more than 150m to less than 100m after using seven parameters for each profile. The resulting lunar global DEM has a significantly improved quality in the local consistencies, i.e. artefacts in the original DEM are eliminated or decreased. The new lunar global DEM is also compared with the laser altimeter data from NASA's LRO mission and JAXA's KAGUYA mission. After comparison, the result shows that the DEMs are consistent and that adjustment does not deform the lunar terrain.