Sub-metre Lunar DEM Generation and Validation from Chandrayaan-2 OHRC Multi-View Imagery Using an Open-Source Pipeline

TL;DR

This paper presents a novel open-source pipeline for generating sub-metre resolution lunar digital elevation models from Chandrayaan-2 OHRC imagery, validated against LRO data.

Contribution

It introduces an open-source method for creating high-resolution lunar DEMs from multi-view OHRC images, including stereo pair selection, dense matching, and validation procedures.

Findings

Generated DEMs with 24-54 cm resolution across five lunar sites.

Achieved vertical RMSE of 5.85 meters compared to LRO NAC terrain.

Horizontal accuracy within approximately 30 centimeters.

Abstract

High-resolution digital elevation models (DEMs) of the lunar surface are essential for surface mobility planning, landing site characterization, and planetary science. The Orbiter High Resolution Camera (OHRC) on board Chandrayaan-2 has the best ground sampling capabilities of any lunar orbital imaging currently in use by acquiring panchromatic imagery at a resolution of roughly 20-30 cm per pixel. This work presents, for the first time, the generation of sub-metre DEMs from OHRC multi-view imagery using an exclusively open-source pipeline. Candidate stereo pairs are identified from non-paired OHRC archives through geometric analysis of image metadata, employing baseline-to-height (B/H) ratio computation and convergence angle estimation. Dense stereo correspondence and ray triangulation are then applied to generate point clouds, which are gridded into DEMs at effective spatial resolutions between approximately 24 and 54 cm across five geographically distributed lunar sites. Absolute elevation consistency is established through Iterative Closest Point (ICP) alignment against Lunar Reconnaissance Orbiter Narrow Angle Camera (NAC) Digital Terrain Models, followed by constant-bias offset correction. Validation against NAC reference terrain yields a vertical RMSE of 5.85 m (at native OHRC resolution), and a horizontal accuracy of within a pixel (approximately 30 cm) assessed by planimetric feature matching.