As title - if aznav processes a line that starts or ends on a grid reference where one component starts with 0 (eg NZ 0429 9739 - Harwood line 6 end), on display it omits the initial zero and displays a three-digit number instead of a four-digit number (eg NZ 429 9739). This can be confusing, though it appears to process correctly.

Have a look at the LIDAR point cloud available in ~arsf/arsf_data/in_progress/2007/flight_data/uk/GB2007_06-2007_192a_Dorchester (lidar/07*).

Attempt to process it into a DEM and any necessary cleanup using GRASS (Environment Agency use GRASS too). Ask me to talk you through the data format (it has some weirdities) before you start.

Compare against the existing NextMAP DEM (tiles sy69,sy78,sy79) to see how 'good' the result is.

Document GRASS procedure on the wiki! (maybe ​http://www.npm.ac.uk/rsg/projects/arsf/trac/wiki/Processing/LIDARDEMs)

Peter Land suggested altering azgcorr to allow L1 files to be opened read-only. Currently they are opened read-write, which causes problems if they are on / were copied from read-only media.