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I have downloaded Lidar data from the UK Environment Agency as ESRI ASCII files but being a complete novice as far as GIS is concerned I do not know how to view them. Quantum GIS was recommended to me so I have installed this. Any help gratefully received.

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You can open directly the asc file in QGIS (Add Raster File):

enter image description here

After that the asc file appears gray:

enter image description here

But if you choose pseudo-colors in the styles (properties of the layer)

enter image description here

The result is

enter image description here

  • True, but qgis wil likely be a lot slower then working with geotiff. – warrieka May 22 '13 at 7:56
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.asc (arcinfo ascii-grid) can be converted to geotiff using the gdal-tools: On the qgis toolbar: Raster/ Conversion / Translate -> Enter the input and output files and if you know it set the srs. Add one creation option to make your output file smaller: COMPRESS - LZW

on the commandline:

gdal_translate -a_srs EPSG:<some_number> -co COMPRESS=LZW -stats <input.asc> <output.tif>

More info: http://www.gdal.org/gdal_translate.html

If your files are very large, you should make overviews as well: Raster/Miscellaneous/Build Overviews

If you have several you want to (virtually) merge: Raster/Miscellaneous/ Merge or Build virtual raster

  • Thanks again - all worked. I have the Lidar images as .asc and .jpeg. I am interested in looking for 'hidden' archaeological features. I thought the .asc files might contain more info but it seems that I can get all I need from processing and viewing the jpegs using PaintShop or PhotoShop which is what I will try next. Thanks again. Alan – Alan Mills May 22 '13 at 7:16
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Try downloading the unlicensed version of Global Mapper (Blue Marble Graphics) which supports extensive viewing options for these ASCII LiDAR files, including ability to vary azimuth and elevation of incident light. I have used it very successfully to detect the archaeological features on a variety of sites in the UK Midlands.

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