False precision in the English Lidar release

Great commentary from Martin Isenburgon of LASTools fame on releasing data with false precision. This deals with the new open data release by the Environment Agency in England. So far LiDAR-derived DTM and DSM rasters have been released for 72% of the entire English territory at horizontal resolutions of 50 cm, 1 m, and 2 m. They can be downloaded here. The rasters are distributed as zipped archives of tiles in textual ASC format (*.asc). 

Martin gives us a cautionary tale on how not to release national data. It is not the ASC format that he has problems with, but the vertical precision. He says:

"The vertical resolution ranges from femtometers to attometers. This means that the ASCII numbers that specify the elevation for each grid cell are written down with 15 to 17 digits after the decimal point."

Example heights might be something like: 79.9499969482421875 or 80.23999786376953125. These data should be resolved to about the cm, not attometer, whatever that is. Crazy man!

Read the full post: http://rapidlasso.com/2015/09/02/england-releases-national-lidar-dem-with-insane-vertical-resolution/