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Topography
Digital Terrain Model (DTM)
A three-dimensional computer-modeled representation of the ground surface, showing the "bare earth" without vegetation and buildings.
A digital terrain model (DTM) is a mathematical representation of the ground surface in digital form, showing the "bare earth" without vegetation, buildings, and other objects. DTM is an essential tool in surveying, construction, and spatial planning.
Types of DTM:
- DTM - "bare" ground surface model
- DSM - Digital Surface Model with all objects
- TIN - Triangulated Irregular Network
- Raster - Regular grid with elevation values
DTM creation methods:
- LiDAR - laser scanning from air or ground
- Photogrammetry - from overlapping photographs
- Tacheometry - traditional point measurements
- GNSS measurements - point coordinate determination
- Existing map digitization - from contour lines
DTM parameters:
- Cell size - 0.5m, 1m, 5m, 10m etc.
- Vertical accuracy - dependent on acquisition method
- Data format - GeoTIFF, ASCII Grid, LAS etc.
- Coverage - territory size
DTM applications:
- Contour generation - for topographic plans
- Volume calculations - earthwork planning
- Flood modeling - flood zone determination
- Slope analysis - slope stability assessment
- Visibility analysis - viewpoint planning
- Road design - route optimization
- 3D visualization - project presentation
DTM precision:
- LiDAR - 5-15 cm vertically
- Drone photogrammetry - 5-20 cm
- Aerial photogrammetry - 15-50 cm
- GNSS measurements - 2-5 cm at points
Latvian DTM:
LGIA provides DTM of Latvian territory created from LiDAR data with 1m cell size. Data is available in the national geospatial infrastructure.