Bare-earth DTM
Definition
A digital terrain model produced by filtering LiDAR returns to ground-level pulses only, removing vegetation and structure returns. The resulting surface represents the actual terrain topography beneath any above-ground cover.
- Data source
- Filtered LiDAR returns at ground-level only
- Resolution capability
- High spatial and vertical resolution
- Key advantage
- Shows actual terrain beneath vegetation and structures
Common questions
What gets removed when creating a bare-earth DTM?+
All above-ground returns are filtered out during processing. This includes vegetation like trees and shrubs, buildings, power lines, and other structures. The model keeps only the ground-level LiDAR pulses that reflect off the actual soil or rock surface.
Why is a bare-earth DTM useful in forensics?+
It reveals the true terrain topography beneath any above-ground cover. This is critical for detecting disturbances or graves that might be hidden by vegetation, or for understanding the landscape when evidence has been concealed.
How is a bare-earth DTM different from a regular DTM?+
A regular DTM may still contain reflections from buildings, vegetation canopy, or other features, making the actual ground harder to see. A bare-earth DTM filters to ground-level pulses only, giving a clean view of the true terrain surface.
Related terms
- Curvature
- A DTM derivative measuring the rate of change of slope. Profile curvature (along the slope direction) identifies convex mounds and concave hollows....
- Ground classification
- The algorithmic process (e.g., using LAStools or PDAL) that separates ground-surface returns from non-ground returns in a LiDAR point cloud, enabling bare-earth...
- Hillshade
- A raster derived from a DTM by simulating illumination from a defined sun position (azimuth and altitude angle). Produces light-and-shadow contrasts that...
- LiDAR
- Light Detection and Ranging: an active remote-sensing method that emits laser pulses and records the time-of-flight of returning echoes to produce a...
- LiDAR (Light Detection and Ranging)
- An active remote sensing technique that emits laser pulses and measures the time of return to calculate distance to reflecting surfaces. Airborne...
- Micro-topography
- Small-scale (centimetre to metre) variations in ground surface height. Grave mounding, subsidence hollows, and soil-scrape scars are micro-topographic features typically invisible to...
- Point cloud
- The raw data product of a LiDAR survey: a set of 3D coordinates (X, Y, Z) for each laser return, classified by...
- Point density
- The number of LiDAR returns per unit area of ground surface, typically expressed as points per square metre. Higher density enables finer...
- SfM point cloud
- A 3D point cloud derived from overlapping photographs using Structure from Motion photogrammetry. Achieves similar resolution to terrestrial LiDAR at close range...
- Terrestrial laser scanning (TLS)
- A ground-based 3D LIDAR survey instrument that captures millions of range measurements per scan to produce a millimetre-accurate point cloud of the...
Explained in these topics
- LiDAR and Topographic SurveyA Digital Terrain Model from which all above-ground returns (vegetation, buildings) have been removed by ground classification, leaving only the modelled groun...
- LiDAR Terrain Analysis for Concealment and DisturbanceA digital terrain model produced by filtering LiDAR returns to ground-level pulses only, removing vegetation and structure returns. The resulting surface repre...