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Digital Mapping

 Digital Mapping

Digital Mapping



2005-03-05
LIDAR - Light Detection and Ranging

LIDAR is an airborne mapping technique which uses a laser to measure the distance between the aircraft and the ground. This technique results in the production of a cost-effective terrain map suitable for assessing flood risk.

The principles of LIDAR The Agency has purchased a LIDAR system which it has installed in a survey aircraft along with its other operational remote sensing instruments, including the compact airborne spectral imager (CASI), a thermal imager, high quality sVHS video camera and a digital camera. The aircraft is positioned and navigated using satellite global positioning (GPS) corrected to known ground reference points.

The aircraft flies at a height of about 800 metres above ground level and a scanning mirror allows a swathe width of about 600 metres to be surveyed during a flight. Individual measurements are made on the ground at 2 metre intervals allowing a highly resolved model of the terrain to be generated.
 
LIDAR coverage map showing areas of England and Wales for which data has been collected.

The Agency's Flood Defence function has a requirement under the Water Resources Act 1991 to monitor the flood plain. LIDAR is being used to measure land topography and assess coastal erosion and geomorphology. The Conservation function requires information on land being set aside for managed retreat of sea defences. There is also a need to obtain data for a model linking land use, soil type and the potential for erosion prediction.



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