Complete Guide to Creation, Applications, and Best Practices
What Is a Digital Terrain Model?
A DTM shows what the landscape would look like if you removed every building, tree, vehicle, and structure. Only the natural ground surface remains, revealing valleys, ridges, slopes, and the true shape of the terrain.
Unlike a Digital Surface Model (DSM) which includes everything visible from above, a DTM uses only ground-classified LiDAR returns to create a bare-earth elevation grid. This makes it essential for any analysis where above-ground objects would interfere.
DTM vs DSM vs DEM
These three terms are frequently confused. Here is how they differ.
| Feature | DTM | DSM | DEM |
|---|---|---|---|
| Shows bare ground | Yes | No | Varies |
| Includes buildings | No | Yes | Varies |
| Includes vegetation | No | Yes | Varies |
| Used for flood modeling | Yes | Rarely | Yes |
| Used for contours | Yes | No | Yes |
| Used for building height | No | Yes | No |
DTM hillshade visualization revealing terrain features in mountainous landscape
How DTMs Are Created from LiDAR
LiDAR provides the most accurate method for DTM creation. Laser pulses penetrate vegetation canopy, reaching the ground underneath trees where photogrammetry cannot.
01
Acquisition
Airborne or drone LiDAR captures millions of elevation points across the survey area.
02
Classification
Algorithms identify ground points versus vegetation, buildings, and noise.
03
Interpolation
Ground-classified points converted to a continuous raster surface.
04
Export
DTM saved as GeoTIFF with hillshade, contours, and slope maps.
TIN (Triangulated Irregular Network) model used for DTM interpolation from ground points
DTM Applications
Agricultural DTM revealing field drainage patterns for precision farming applications
Resolution and Accuracy
| Application | Resolution |
|---|---|
| Regional flood modeling | 5–10m |
| Site engineering | 0.5–1m |
| Detailed construction | 0.1–0.25m |
| Archaeological survey | 0.25–0.5m |
Vertical accuracy depends on source data: airborne LiDAR achieves 5–15 cm RMSE, drone LiDAR with GCPs reaches 3–10 cm, and photogrammetry in open terrain yields 10–50 cm.
Classification Accuracy Matters
DTM quality depends entirely on accurate ground classification. Common challenges include:
- Dense vegetation: limited ground returns under thick canopy
- Complex terrain: steep slopes can confuse classification algorithms
- Low structures: cars, fences, and walls may be misclassified as ground
- Water surfaces: LiDAR struggles with specular water reflections
Lidarvisor’s automatic classification handles these challenges, correctly identifying ground points in diverse terrain conditions.
Creating DTMs with Lidarvisor
Lidarvisor automates the entire DTM workflow:
- Upload your LAS or LAZ point cloud
- Automatic classification identifies ground, vegetation, and buildings
- DTM generation creates bare-earth terrain from ground points
- Derivative products: hillshade, contours, and slope maps generated automatically
- Download as GeoTIFF, DXF contours, or classified point cloud
No GIS expertise required. Upload your data and receive survey-ready terrain products in minutes.
Free DTM Data Sources
Before creating your own DTM, check if free public data meets your needs.
USGS 3DEP (United States)
The most comprehensive elevation coverage for the US. Quality Level 2 provides 1-meter resolution with 10cm vertical accuracy. Access through The National Map.
EU Copernicus DEM (Global)
30-meter and 90-meter global coverage from TanDEM-X radar data. Suitable for regional analysis and watershed studies. Available through the Copernicus Space Data Ecosystem.
SRTM (Global)
30-meter data for most of the world. Note: SRTM is technically a DSM, not a DTM, as it includes vegetation and building heights.
National Programs
- UK Environment Agency: 1m DTM covering England
- Australia Elvis: Various resolution DEMs
- OpenTopography: Curated LiDAR datasets worldwide
Frequently Asked Questions
DTM specifically means bare-earth terrain with all objects removed. DEM is a generic term for any elevation grid. In practice, the terms are often used interchangeably, especially in the United States where DEM typically refers to bare-earth data.
Use DTM when you need the actual ground surface for hydrology, engineering, or any application where buildings and trees would interfere with analysis. Use DSM when above-ground features matter, such as urban planning, telecommunications, or forestry canopy analysis.
Yes, but with limitations. Photogrammetry produces a DSM first, then filtering algorithms attempt to remove vegetation. Results are less accurate under tree canopy since cameras cannot see through vegetation like LiDAR can.
DTMs are typically stored as GeoTIFF, georeferenced raster images where each pixel contains a ground elevation value. Other formats include ASCII grid, ESRI Grid, and LAS/LAZ classified point clouds. Lidarvisor exports DTMs as GeoTIFF compatible with all major GIS software.
LiDAR DTMs typically achieve 5–15 cm vertical accuracy depending on sensor quality, flight parameters, and ground conditions. Drone LiDAR with ground control points can achieve 3–10 cm accuracy. Classification quality affects final DTM accuracy as poorly classified data produces less accurate terrain models.