From CUDEM to Continuous DEMs: Building an Open-Source Ecosystem for Digital Elevation Models

Digital Elevation Models (DEMs) are fundamental inputs for tsunami and flood modeling, coastal planning, infrastructure assessment, and many other Earth-science applications. Coastal DEMs commonly integrate airborne and topobathymetric lidar, hydrographic surveys, existing elevation models, and other measurements that differ in resolution, accuracy, coordinate systems, vertical datums, spatial coverage, and accessibility. Building an accurate, reproducible DEM therefore requires more than interpolating elevations. Source measurements must be identified and processed, transformed to a common reference system, integrated according to their characteristics and relative suitability, their contributions to the final surface preserved through provenance, and the resulting DEM evaluated with independent measurements.

The Continuously Updated Digital Elevation Model (CUDEM) framework was developed through NOAA’s National Centers for Environmental Information and the Cooperative Institute for Research in Environmental Sciences to make these steps more systematic and repeatable. CUDEM consisted of modular command line interface (CLI) tools for data discovery, elevation processing, vertical datum transformation, gridding, provenance, and related DEM-development tasks within a single open-source framework and supported NOAA coastal DEM production and research, including the systematic tiled CUDEMs described by Amante et al. (2023).

Our NSF Pathways to Enable Open-Source Ecosystems (POSE) Phase I project examined how this scientific and software foundation could grow into a broader open-source ecosystem. More than 140 interviews with potential users, contributors, collaborators, software developers, data providers, and representatives of related Earth-science and open-source communities identified recurring barriers involving installation and onboarding, documentation and support, contribution pathways, and long-term maintenance. These findings helped drive the transition from CUDEM to Continuous DEMs, in which major responsibilities are distributed across distinct but connected projects: Fetchez provides geospatial data access and the shared workflow framework; Transformez provides horizontal and vertical reference-system transformations for elevation data; Globato provides DEM production, source integration, and provenance; and IVERT evaluates DEM elevations with independent ICESat-2 measurements. This reorganization preserves the scientific principles established through CUDEM while making individual capabilities easier to use, test, contribute to, and maintain. Operational DEM production, workshops, external collaborations, and downstream applications are beginning to extend the software, workflows, and knowledge beyond the original development team. The goal is to broaden participation and responsibility without weakening the scientific quality and reproducibility required for DEM development.