In the geospatial industry, acronyms like DEM, DSM, and DTM are frequently used when referring to elevation data, but they aren’t interchangeable. A Digital Elevation Model (DEM) is a general term for a raster representation of elevation values, most often referring to a bare-earth surface. A Digital Surface Model (DSM) represents the top of the Earth’s surface, including buildings, vegetation, and other above-ground features. A Digital Terrain Model (DTM) specifically represents the underlying ground surface, with structures and vegetation removed.
Digital Terrain Models are essential for analyses such as hydrology modeling, slope and contour generation, earthwork calculations, and any workflow where an accurate representation of the true ground surface is required. In the sections that follow, we’ll walk through how to create a DTM in Global Mapper®, including optimizing parameters, choosing gridding methods, and applying best practices for point cloud–based modeling.
Making a Digital Terrain Model in Global Mapper
The Elevation Grid Creation tool in Global Mapper uses any 3D vector data to generate a gridded raster elevation layer, including digital terrain models. DTMs can be made in just a few steps: load your elevation data, open the Create Elevation Grid tool, choose a binning method, and click OK. Once created, terrain models can be visualized, edited, analyzed, and exported in one of the many supported elevation formats– all within Global Mapper.
In practice, DTMs are commonly derived from lidar or other 3D data sources by isolating ground measurements and interpolating them into a continuous surface. When creating a DTM from a point cloud, it’s best to first classify the ground using Global Mapper Pro’s point cloud classification tools. Available within the Point Cloud Analysis tool, the ground classification process automatically identifies and labels likely ground points. When generating the elevation grid, you can then filter by classification to exclude non-ground points, ensuring the resulting surface accurately represents the terrain.
Choosing the Right Gridding Method
When creating an elevation grid, the Create Elevation Grid dialog offers multiple methods for interpolating 3D vector data into a continuous surface. The two primary approaches are Triangulated Irregular Network (TIN) and Binning methods. Understanding how each method works will help you choose the best option for your data and analysis goals.
The image below provides a visual comparison of elevation grids generated from the same data using different methods, shown along a common path in the Path Profile tool. In this example, the binning method produces a smoother surface than the triangulated method. While both approaches are widely used, binning is the more popular choice overall. There is ongoing debate within the industry about which method offers higher accuracy, but the answer largely depends on how accuracy is defined and how the resulting surface will be used. Ultimately, the best method is the one that meets the needs of your specific project.
