# Archiving and Distribution of High-Quality SOCET SET Context Camera (CTX) Digital Terrain Models

Matthew Chojnacki, Sarah S Sutton, Susan J. Conway, Joel Davis, Axel Noblet, Daven Quinn

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## To cite this version:

Matthew Chojnacki, Sarah S Sutton, Susan J. Conway, Joel Davis, Axel Noblet, et al. Archiving and Distribution of High-Quality SOCET SET Context Camera (CTX) Digital Terrain Models. 56th Lunar and Planetary Science Conference, LPI, Mar 2025, The Woodlands (Texas), United States. hal-05395700

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Submitted on 3 Dec 2025

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**ARCHIVING AND DISTRIBUTION OF HIGH-QUALITY SOCET SET CONTEXT CAMERA (CTX) DIGITAL TERRAIN MODELS.** M. Chojnacki¹, S. S. Sutton², S. Conway³, J. Davis⁴, A. Noblet⁵, D. Quinn⁶.

¹Planetary Science Institute, Lakewood, CO (mchojnacki@psi.edu); ²Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ; ³Laboratoire de Planétologie et Géosciences, Nantes, France; ⁴Birkbeck, University of London, England. ⁵University of Western Ontario, ON, Canada; ⁶University of Wisconsin, Madison, WI.

**Introduction:** High-resolution topography and imaging have radically advanced our knowledge of the environmental conditions and geologic processes shaping planetary surfaces. For example, topography and associated visible-wavelength data enables geologic and structural mapping, insight into crustal thickness, and the identification of potential hazards for surface operations. Many locations on Mars have available stereo image coverage but lack sufficient topographic data. This 2022 *Planetary Data Archiving, and, Restoration* (PDAR) funded effort will deliver hundreds of high-quality digital terrain models (DTMs) and orthoimages of the surface of Mars from the Mars Reconnaissance Orbiter's *Context Camera* (CTX) (1) to the planetary community in widely accessible formats. The purpose of this abstract is to inform on our efforts to distribute CTX topography to the science community.

**Need for CTX DTM Repository:** The current state of community CTX DTM products is highly variable in terms of format, volume, and quality. The U.S. Geological Survey (USGS) has produced special release CTX topography annexes for select missions like *Mars 2020* (https://astrogeology.usgs.gov/Mars2020/) and *InSight* (2–4), which are high quality but are limited in number. The Pacific Regional Planetary Data Center at the University of Hawai‘i has produced quality CTX DTMs of craters, volcanoes, and other landforms (https://www.higp.hawaii.edu/prpdc/CTX_DEMs/tople vel.html)(5). The *MarsSI* platform (https://marssi.univ- lyon1.fr/MarsSI/) has implemented the automated mass

derivation of the Ames Stereo Pipeline (6) for HiRISE and CTX DTMs (7). Although potentially useful for a careful user utilizing a quality stereo pair (8), these ASP products are not edited or validated for the user, nor are confidence maps provided. Additional CTX DTMs can be found associated with various published articles, but again there is no standard practice or uniform search engine to find these data such as the ODE. This effort seeks to remedy these issues.

<figure><img src="image_3.png" /><figcaption>**Figure 1.** Global map of Mars displaying the locations of the 288 CTX DTMs. Regions with some of the greatest coverage include: (a) Oxia and Mawrth Vallis; (b) Valles Marineris; (c) Nereidum Montes. Base maps are MOLA hill shade with grayscale topography (90°N-60°S).</figcaption></figure>

**Existing CTX Archive:** Our data products have been generated using BAE Systems SOCET SET® photogrammetry software, a platform that has become the community standard for high-quality topographic data production (e.g., landing site certification, landscape modeling, surface monitoring) (4, 9). These

<figure><img src="image_4.png" /><figcaption>**Figure 2.** Examples of CTX PDS DTM supplementary “EXTRAS” products for DTEEZ_024127_1673_024483_1673_A01. Each DTM is rendered as a reduced, compressed (.png) image with annotations for the product ID, image credit, and scale bar, and non-annotated browse and thumbnail images. All images shown are north up, with illumination from the upper left. From left to right: gray-scale image of DTM (lighter values are increasing elevation), colorized elevation over shaded relief (purple is low, white is high), shaded relief map, orthoimage, Figure of Merit (FOM) map and FOM legend. Stereo data are G15_024127_1673_XN_12S181W & G16_024483_1673_XN_12S181W.</figcaption></figure>
CTX DTM s are processed at ~20 m/elevation post and orthoimages at 6 and ~20 m/pixel. In most cases, the stereo images have been registered to the standard reference frame of Mars Orbiter Laser Altimeter (MOLA) data. A post-by-post quality classification map of the of the DTM will be include as a Figure of Merit (FOM) raster. These CTX DTM s provide important context for higher resolution High Resolution Imaging Science Experiment (HiRISE) data, including many co-registered HiRISE DTM s. These data products have already been generated and are awaiting a suitable publicly accessible repository that adheres to Planetary Data Systems (PDS) standards. Our CTX DTM SOCET SET® to PDS pipeline is modeled after and complementary to those for the HiRISE PDS archive, compliant with PDS4 archiving standards (10).

**Objective 1: Create the CTX DTM SOCET SET® to PDS pipeline:** The main objective here is to create the post-processing workflow to translate the exported files from the SOCET SET-ISIS processing chain to PDS4-compliant formats (legacy PDS3 to be included as Supplemental files). Starting with the SOCET SET exported RAW formatted data and shell scripts in-house Perl script will be run that create the PDS-formatted files and labels. These will be 32-bit (DTM) and 8-bit (orthoimage) rasters in PDS4-compliant GeoTIFF format (11) and range in size from 30-120 MB depending on the scale and length. All PDS4 and supplemental products will be accompanied by a detached XML label. List of STANDARD PRODUCTS include (for DTM s, Orthoimages, Figure of Merits): GeoTIFF/.tif, Text/.xml. List of SUPPLEMENTAL PRODUCTS include (for DTM s): Image/.IMG, Text/.xml; (Orthoimages): GeoJP2/.JP2 Text/.LBL; (Browse images): PNG/.png, Text/.xml. Sample Products will be provided to the PDS Cartography and Imaging Sciences Node for review to identify any issues. We will also set up a process to deliver the finalized bundles to the PDS.

**Objective 2 & 3: Process, validate, and release UA- and Co-investigator-produced CTX DTM s to PDS:** For us to generate the Objective 2 University of Arizona (UA) produced CTX DTM products and eventually deliver these to the PDS for public use, several processing/validation steps must be performed on the SOCET SET-derived data. The processing and validation steps are: configuration file generation, run script to generate the PDS-formatted files and labels from SOCET SET files, product validation, data delivery and archiving with the PDS. This step will be repeated for Objective 3 DTM s to be archived by our co-investigators and their institutions: Laboratoire de Planétologie et Géosciences (LPG, France), Birkbeck, University of London (BBK, England), and University of Wisconsin (UW). There are

hundreds of existing CTX DTM s that are expected to be processed, validated, and released to the PDS.

**Objective 4: Publish final documentation of SOCET SET® to PDS pipeline:** Following the completion of data archiving, our team will publish a description of our CTX DTM data production and their effectiveness in addressing science investigations needing moderate-resolution topography in an Open-Access journal. Once the data are archived, we will work with the Java Mission-planning and Analysis for Remote Sensing (JMARS) (https://jmars.mars.asu.edu/)(12) Team who will provide a data portal on their GIS platform.

**Project Status:** To date we have refined the CTX DTM PDS3 and PDS4 data products, which largely mirrors that of HiRISE PDS4 standards. Critically, HiRISE has received final confirmation on formatting of RDR and DTM products from the PDS and will begin producing PDS4 data in 2025. Accordingly, we have creating configuration files for processing of CTX DTM projects, which include all necessary keywords for PDS product generation. UA CTX projects and been collected and prepped for further processing. Initial test products have been obtained from the external LPG, BBK, UW Co-investigators. In 2025 we will begin delivering products to the *Cartography and Imaging Sciences Node* for review.

Finally, if there are additional institutions with photogrammetry labs who have implemented SOCET SET software to produce CTX DTM s there is the possibility of collaboration with this effort. Inquiries should be made to the primary author of this abstract. Unfortunately, we cannot accept non-SOCET SET DTM s produced with Ames Stereo Pipeline or other platforms.

**Acknowledgments:** This research was supported by NASA PDAR Grant 80NSSC21K1096.

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