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There were two sources of ground elevation data used within this trial, the Environment Agency (EA) LiDAR and Ordnance Survey Terrain 5 data. The EA [6] offer LiDAR data with a spatial resolution of between 25 cm and 2 m. It is currently stated by the EA that accurate elevation data is available for over 75% of England. The absolute height error is quoted to be less than ±15 cm. This is the root mean square (RMS) error. The Ordnance Survey (OS) Terrain 5 data [7] has a quoted height error of ±1.5 m. This is the RMS error for urban and major communication routes. For rural and mountain and moorland areas the error is higher at ±2.5 m. The spatial resolution for all OS Terrain 5 data is 5 m. Figure 2: Example Depth of Cover Report (Aerial imagery source: Esri, DigitalGlobe, GeoEye, Earthstar Geographisc, CNES/Airbus DS, USDA, USGS, AeroGRID, IGN and the GIS User Community) Figure 1: Example of points provided from post inspection data processing RESEARCH / DEVELOPMENT / TECHNOLOGY Given the better spatial resolution and greater accuracy of the EA LiDAR data, this was the preferred dataset for use in this trial. However, examination of the available EA LiDAR data identified that there was not full data coverage of the trial pipeline. A 6 km missing section of EA LiDAR data was supplemented with OS Terrain 5 data for the trial.