Abstract
Topographic products are important for mission operations and scientific research in lunar exploration. In a lunar rover mission, high-resolution digital elevation models are typically generated at waypoints by photogrammetry methods based on rover stereo images acquired by stereo cameras. In case stereo images are not available, the stereo-photogrammetric method will not be applicable. Alternatively, photometric stereo method can recover topographic information with pixel-level resolution from three or more images, which are acquired by one camera under the same viewing geometry with different illumination conditions. In this research, we extend the concept of photometric stereo to photogrammetric-photometric stereo by incorporating collinearity equations into imaging irradiance model. The proposed photogrammetric-photometric stereo algorithm for surface construction involves three steps. First, the terrain normal vector in object space is derived from collinearity equations, and image irradiance equation for close-range topographic mapping is determined. Second, based on image irradiance equations of multiple images, the height gradients in image space can be solved. Finally, the height map is reconstructed through global least-squares surface reconstruction with spectral regularization. Experiments were carried out using simulated lunar rover images and actual lunar rover images acquired by Yutu-2 rover of Chang’e-4 mission. The results indicate that the proposed method achieves high-resolution and high-precision surface reconstruction, and outperforms the traditional photometric stereo methods. The proposed method is valuable for ground-based lunar surface reconstruction and can be applicable to surface reconstruction of Earth and other planets.
Highlights
In lunar exploration, topographic mapping products, such as digital elevation model (DEM) and digital orthophoto map (DOM), are important for mission operations and scientific research
This paper proposes a novel photogrammetric-photometric stereo (PPS) method based on the collinearity equation and reflectance model for ground-based mapping of the lunar surface
Quantitative measures of DEMs by three methods for Yutu-2 the height map from multiple rove images taken by a single camera under the same Methods viewing geometry with changing illumination conditions
Summary
Topographic mapping products, such as digital elevation model (DEM) and digital orthophoto map (DOM), are important for mission operations and scientific research. 2021, 13, 2975 camera, which is located on top of the lander [10] It can rotate 360◦ horizontally to obtain a panoramic view of the lunar surface, but without stereo imaging capability. Photometric stereo techniques have been developed for lunar and planetary surface reconstruction [14,15,16,17,18] to improve the quality of mapping products and generate pixel-level DEMs where image matching fails [14,19]. It would be valuable to integrate photometric stereo with collinearity equations and lunar reflectance model for rover image-based surface reconstruction when stereophotogrammetric method is not applicable. This paper proposes a novel photogrammetric-photometric stereo (PPS) method based on the collinearity equation and reflectance model for ground-based mapping of the lunar surface.
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