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.
.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
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.