Getmapping Height Data
This is derived from our own digital aerial photography and the result of a DTI funded Knowledge Transfer Project between Getmapping, Bath Spa University, GeoSense and SCS. The partnership seeks to create an enhanced Digital Elevation Model (eDEM) of the whole of the Britain using workflows and algorithms, which require little if any human interaction. Significantly the data is produced at a 1 metre posting, which exceeds the 2m posting normally used in LiDAR. The result is probably the best balance between cost and accuracy currently available with the significant added bonus of nationwide coverage, which is not available for LiDAR. For practical comparison the Getmapping height data is within a few centimetres of LiDAR in open areas but is actually better than LiDAR when it comes to building heights, which are the result of photogrammetry.
The availability of matching aerial photography provides working ‘intelligence’ and the ability to create 3D environments for further investigation or display.
Getmapping height data is available as a Digital Surface Model (DSM), Digital Terrain Model (DTM) and contours.
Digital Surface Model (DSM)
The first surface model is produced using the digital stereo aerial photography acquired by Getmapping. The data is acquired and processed independent of any OS datasets and is therefore free from any third party copyright. The process takes advantage of semi-automatic algorithms and the superior quality of the digital camera technology to produce a clean first surface model. This requires only minimal manual editing to remove gross errors. The result is a DSM with a 1m posting and a vertical accuracy RMSE of up to 40cm with sub-pixel horizontal accuracy. For practical comparison the accuracy of ‘heighting’ in open areas is directly comparable with LiDAR.
Digital Terrain Model (DTM)
The DSM is edited to produce the 1m DTM product. Getmapping uses a suite of algorithms to semi-automatically edit the DSM and remove unwanted surface features. These algorithms include a routine, which reduces the woodland canopy areas based on a bounding polygon. This requires some manual intervention to create bounding polygons for woodland extents. In addition, break lines are captured where required to ensure true terrain features are not removed and that bodies of water, such as lakes, remain flat. The result is a 1m posted DTM with a vertical accuracy of up to 50cm RMSE.
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email us at: sales@getmapping.com