Enhanced Digital Terrain Model height data

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

More useful links

• Enhanced DTM sample data
• Price lists
• Online Map Shop