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Author Topic: UK LIDAR data  (Read 544 times)

PeterC

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UK LIDAR data
« on: 13 February 2016, 14:57:12 »
LIDAR data for the UK (but only England for now) is available for free download from the government's GeoStore. There is an article Lasers reveal 'lost' Roman roads about how "Archaeologists are using Environment Agency laser mapping data to rediscover hundreds of kilometres of 'lost' Roman roads". An earlier article on Free mapping data will elevate flood risk knowledge gives more details on how LIDAR is used to help the work of the Environment Agency.

I do not find this site easy to use so have added some notes below (and the FAQs have more useful details).

Notes on LIDAR
  • To get data go to the Geostore survey page and select the grid square you want
  • Choose whether you want
    • DTM - the Digital Terrain Model (or bald earth model) which shows the ground of the earth and nothing else; no houses, buildings or vegetation
    • DSM - the Digital Surface Model which shows features such as buildings and trees
  • Note that Lidar does not penetrate water, therefore the surface of a lake will appear flat in the DTM
  • Choose whether you want
    • Tiles (for some areas there are repeat surveys and data is available in a range of resolutions)
    • Composite (recommended: derived from a combination of tiles to give the best possible spatial coverage)
  • Choose whether you want 2 meter, 1 metre, 50 cm, or 25 cm horizontal spaced data (depends on what is available for your square)
    • As an example, 2 metre horizontal spaced data means a Lidar point has been acquired once every two metres (the data is built up into a grid of points)
  • The Lidar data is delivered in a zip file with multiple tiles in ASCII Grid format and needs special software to view
    • You can pick out the particular (1 km square) tiles you want
    • I am using QGIS to visualise the data and have found this article on Geographic Information Systems Stack Exchange helpful guidance in this process (however it has been trial and error)
    • I have managed to use QGIS to get reasonable images (see one attached), and will post how I did it if anyone is interested
  • These Lidar scans have been found "to be better than +/- 15cm vertically and +/- 43cm horizontally", but are only at less than 1m spaced in areas prone to flooding
Other data and images

Geostore also offers for sale photographic prints (framed or unframed) and digital files (jpeg/TIFF/ECW) - all orthorectified, geo-referenced and accurate to +/- 2 metres - for the home user; and many varieties of aerial photography data, height data, maps and geographic business intelligence available to commercial organisations. To buy any of these click on Buy Now and select your location.

These files come either as a tile or a mosaic:
  • A tile is a one square kilometre area of aerial imagery, consistent with those used by the Ordnance Survey National Grid system.
  • A mosaic is when these “tiles” are stitched together to form one image.
« Last Edit: 2 March 2016, 19:58:05 by PeterC »

 

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