An Optimized Method for Terrain Reconstruction Based on Descent Images

Abstract

Abstract. An optimization method is proposed to perform high-accuracy terrain reconstruction of the landing area of Chang'e III. First, feature matching is conducted using geometric model constraints. Then, the initial terrain is obtained and the initial normal vector of each point is solved on the basis of the initial terrain. By changing the vector around the initial normal vector in small steps a set of new vectors is obtained. By combining these vectors with the direction of light and camera, the functions are set up on the basis of a surface reflection model. Then, a series of gray values is derived by solving the equations. The new optimized vector is recorded when the obtained gray value is closest to the corresponding pixel. Finally, the optimized terrain is obtained after iteration of the vector field. Experiments were conducted using the laboratory images and descent images of Chang'e III. The results showed that the performance of the proposed method was better than that of the classical feature matching method. It can provide a reference for terrain reconstruction of the landing area in subsequent moon exploration missions. Keywords:Chang'e III; descent images; feature point extraction; geometric constraint; terrain reconstruction. IntroductionIn lunar exploration, high-precision terrain reconstruction of the landing area has significance for achieving the scientific objectives of future projects and is important for safety and efficient path planning of the rover [1]. The Chang'e II detector acquired a large number of lunar images and other information in previous lunar exploration projects. Digital orthophoto maps with 1.5 m resolution and digital elevation models with 4 m resolution are currently being produced using the existing images captured by the Chang'e II satellite [2][3][4]. However, a terrain reconstruction with this accuracy can only be used for macro scientific investigation and cannot be used for path planning of the rover of Chang'e III [5]. The navigation cameras attached to the Chang'e III rover have a high resolution and can provide the basis for high-precision terrain reconstruction. However, the use of navigation cameras was not conducive to