Enhanced Digital Terrain Model height data
An Enhanced Digital Terrain Model (DTM) is a digital file showing break-lines and spot heights. Break-lines show changes in slope for cliffs and road embankments. An enhanced DTM provides a detailed representation of the topographical variations in the earth's surface.
Updating the data
Enhanced DTMs are updated within the same cycle as the orthophotography:
Information about the enhanced DTM
The enhanced DTM has a point file of heights, along with break-lines showing differences in height. The enhanced DTM data features are:
- suitable for digital creation of 3D mapping such as slope and aspect maps
- using Geographical Information software, orthophotographs and maps, it can be draped over a Triangular Irregular Network (TIN) derived from a DTM to create a 3D view of the land surface
- can be used in a GI software to create thematic maps, grids and contours
- can be used in the electronic process of representing topography in three dimensions for example in a Geographical Information or CAD system
Where to use an enhanced DTM
An enhanced DTM is suitable for applications in:
- planning
- engineering
- visualisation
- height analysis
- environmental impact analysis
- sight lines
- wind flow and pollution dispersion
- soil erosion modelling
- flow direction and accumulation
- watershed delineation
Technical information
The enhanced DTM is created from stereo imagery in the orthophotography production process. It has:
- DXF format
- 60m point spacing with break-lines for notable changes in slope
- all height measurements in metres mean above sea level at Belfast Lough
- an accuracy of 1.0m RMSE (root means square error) - 65 per cent of data has an accuracy of 1.0m, 90 per cent has an accuracy of 2.0m, and 99 per cent of the data has an accuracy of 3.0m