Abstract

Abstract. The present availability of sub-decametre digital elevation models on Mars – crucial for the study of surface processes – is scarce. In contrast to low-resolution global datasets, such models enable the study of landforms <10 km in size, which is the primary scale at which geomorphic processes have been active on Mars over the last 10–20 Myr . Stereogrammetry is a means of producing digital elevation models from stereo pairs of images. The HiRISE camera on board the Mars Reconnaissance Orbiter has captured >3000 stereo pairs at 0.25 m pixel−1 resolution, enabling the creation of high-resolution digital elevation models (1–2 m pixel−1). Hitherto, only ∼500 of these pairs have been processed and made publicly available. Existing pipelines for the production of digital elevation models from stereo pairs, however, are built upon commercial software, rely upon sparsely available intermediate data, or are reliant on proprietary algorithms. In this paper, we present and test the output of a new pipeline for producing digital elevation models from HiRISE stereo pairs that is built entirely upon the open-source NASA Ames Stereo Pipeline photogrammetric software, making use of freely available data for cartographic rectification. This pipeline is designed for simple application by researchers interested in the use of high-resolution digital elevation models. Implemented here on a research computing cluster, this pipeline can also be used on consumer-grade UNIX computers. We produce and evaluate four digital elevation models using the pipeline presented here. Each are globally well registered, with accuracy similar to those of digital elevation models produced elsewhere.

Highlights

  • After several decades of orbital study, Mars is well served by remotely sensed imagery

  • The AU pipeline is designed to be freely implemented, and as such we describe only those pipelines making use of open-source software and refer readers to Tao et al (2018) for a summary of the existing SOCET-SET pipeline for the production of High Resolution Image Science Experiment (HiRISE) digital elevation models (DEMs) released on the Planetary Data System Orbital Data Explorer (PDS ODE)

  • In order to evaluate the uncertainty in the DEMs produced by our pipeline, we calculated the root mean square error (RMSE) between HiRISE AU DEMs and those already available from the PDS ODE, both against each other and against the lower-resolution High Resolution Stereo Camera (HRSC) and Mars Orbiter Laser Altimeter (MOLA) DEMs

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Summary

Introduction

After several decades of orbital study, Mars is well served by remotely sensed imagery. DEMs can be made using higher-resolution imagery; HRSC DEMs, while valuable in their own right, serve as a resolution bridge between the coarse MOLA DEM and DEMs produced using the higher-resolution Mars Reconnaissance Orbiter Context Camera (CTX: 6 m pixel−1; Malin et al, 2007) and High Resolution Image Science Experiment (HiRISE: 25–50 cm pixel−1; Mcewen et al, 2007) imagery. In this paper we present and test an open-source and largely automated processing pipeline for the production of well registered and globally accurate DEMs from stereo pairs of HiRISE and CTX images, referred to hereafter as the Aberystwyth University pipeline (AU pipeline).

The ASP method
Bundle adjustment
The Chicago method
Stereo DEM production by the CASP-GO method
Development of near-automatic open-source AU workflow
The AU method
Evaluating the AU pipeline
Comparison 1
Comparison 2
Comparison 3
Comparison 4
DEM artefacts
Case study – evaluating AU DEM 2
Summary and conclusions
AU DEM 1
AU DEM 3
AU DEM 4
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