Abstract | Accurate 3D models are essential for geomorphologic analysis, reflectance modeling, and spectral analysis. Our group developed a Shape-from-Shading (SfS) algorithm to create digital terrain models (DTMs) of the Lunar (1) and the Martian surface (2). Recently, we refined our Shape from Shading (SfS) algorithm to generate high-resolution DTMs of Mercury from MESSENGER imagery (3). To adapt the reconstruction procedure to the specific conditions of Mercury and the available imagery, we introduced two methodic innovations. First, we extended the SfS algorithm to enable the 3D-reconstruction from image mosaics. Because most mosaic tiles were acquired at different times and under various illumination conditions, the brightness of adjacent tiles may vary. We found that the relaxation of the constraint for a continuous albedo map improves the topographic results of an extensive region yields seamless transitions at tile borders. The second innovation enables the generation of accurate DTMs from images with substantial albedo variations, such as hollows. We employed an iterative procedure that initializes the SfS algorithm with the albedo map obtained by the previous iteration step. This approach converges and yields a reasonable albedo map and topography. We generated DTMs of several science targets such as the Rachmaninoff basin, Praxiteles crater, fault lines, and several hollows with these approaches. We compared our DTMs with stereo DTMs and laser altimeter data to evaluate the results. In contrast to coarse laser altimetry tracks and stereo algorithms, which tend to be affected by interpolation artifacts, SfS can generate DTMs almost at image resolution. The root mean squared errors (RMSE) at our target sites are below the size of the horizontal image resolution. For some targets, we could achieve an effective resolution of less than ten m/pixel, which is the best resolution of Mercury to date.
(1) Grumpe, A., Wöhler, C., 2014. Recovery of elevation from estimated gradient fields constrained by digital elevation maps of lower lateral resolution. ISPRS Journal of Photogrammetry and Remote Sensing, 94, 37 - 54. https://doi.org/10.1016/j.isprsjprs.2014.04.011
(2) Hess, M., Wohlfarth, K., Grumpe, A., Wöhler, C., Ruesch, O., and Wu, B.: ATMOSPHERICALLY COMPENSATED SHAPE FROM SHADING ON THE MARTIAN SURFACE: TOWARDS THE PERFECT DIGITAL TERRAIN MODEL OF MARS, Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XLII-2/W13, 1405–1411. https://doi.org/10.5194/isprs-archives-XLII-2-W13-1405-2019, 2019.
(3) Tenthoff, M.; Wohlfarth, K.; Wöhler, C. High Resolution Digital Terrain Models of Mercury. Remote Sens. 2020, 12, 3989. https://doi.org/10.3390/rs12233989
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