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February 2001
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Flood alert all mapped out by Ordnancesurvey
LIDAR (Light Detection and Ranging) is an airborne mapping technique, using a laser to measure the distance between the aircraft and the ground by calculating the speed and intensity of the returning signal. The 3-D digital elevation models of the landscape created by LIDAR are highly detailed and closely match every undulation on the ground, including man-made and natural features such as trees, buildings, quarries and landfill sites.
Using LIDAR, flood plain mapping and prediction models can be used to show the possible extent of flooding, depending on rainfall levels. In light of the recent increase in flooding throughout the country, this is likely to prove an invaluable tool, not only for the Environment Agency in planning defences but also for insurance companies, builders and developers.
As it is accurate to within 190 mm (about 8 inches), LIDAR can also be used to study flood defence structures, changes along coastlines and the rate of deposition in landfill sites. Drainage directions and soil erosion rates can also be predicted.
The planning of new developments, road schemes, forestry and horticulture can also benefit from the accuracy that LIDAR brings to three-dimensional mapping as, when overlaid with Ordnance Survey's digital mapping such as its highly detailed Land-Line data, it clearly displays the visual impact that new features will make on the landscape.
"Using the LIDAR data on its own is very effective when measuring the height and depth of features on the ground. But when overlaid with Ordnance Survey's highly detailed digital mapping data, the features are identified and neatly labelled, bringing the whole model to life," says Kirstie Bulpitt, Ordnance Survey's Land-Form Product Manager.
"With such highly effective and accurate digital data, cost is always a factor. But when viewed against the potential savings in avoiding or preventing serious flooding, LIDAR is not only very valuable but also extremely cost-effective," she adds.
Major flood plain areas, coastlines, urban conurbations and river valleys are already available as LIDAR data, while anywhere else in Britain can be recorded to order.
Details of available areas are listed on the Ordnance Survey web site at www.ordnancesurvey.co.uk/productpages/lidar/home.htm
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