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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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What/Where was your source for the Lidar files? –  Mapperz May 21 '13 at 18:22
    
The source of the Lidar data was the Geomatics Group of the Environment Agency –  Alan Mills May 21 '13 at 20:49
    

2 Answers 2

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

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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

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True, but qgis wil likely be a lot slower then working with geotiff. –  warrieka May 22 '13 at 7:56

.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

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Thanks very much. I will try this tomorrow. –  Alan Mills May 21 '13 at 20:50
    
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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