Comparison of lidar dems

We patch lidar data on to ASTER data during delivery creation and need to know how accurately that data has been patched and, if it is differing, to what level it differs.

To do this we can use:

demcompare.py -d lidarpatched.dem -n navfile.sol --lidar path/to/ascii

This will create a patched aster dem to compare to the lidar dem, this will not be smoothed and as such is the raw ASTER data. It will give 2 outputs on completion the first is only the area covered by the lidar files, the second is the area only covered by the lidar data. All outputs are in metres.

Preferably the averages would be around 0 metres, but in practice it tends to be around 4 - 8 metres for UK data and varying for UTM data.

You can compare 2 dems already created using

demcompare.py -d dem1.dem -c dem2.dem --lidar /if/needed

Which will skip the patching process and just give the dem outputs, if you ude identical dems the outputs will be 0.