Frequently Asked Questions

Hyperspectral Data and Deliveries

• I have no ground truth reflectance data - how can I convert my radiance to reflectance?
• What do the tags in the line and project information XML files mean?
• How do I convert the data type of BIL files to floats?
• Why are the level 3 files so large when they are unzipped?

• What are the bandwidths/band centres of my data?
• My data values are much larger than I was expecting. What units are the data in?

APL

• What is the difference between APLCorr and Azgcorr?
• What do the values in my mask file represent?
• Why does my mapped image have black bars across track?
• What format should my DEM be in when using aplcorr?
• I get the error "unrecognised options on command line:", what does this mean?
• Where can I get the grid shift file needed for apltran for describing the Ordnance Survey National Grid projection?
• I get the error "Unknown map projection: You will have to fill in the projection name and datum in the map info in the .hdr file yourself." when defining a projection using Proj4, what should I do?

LiDAR Data

• What is the file format for my ASCII LiDAR data files?
• How do I convert between LAS and ASCII file formats?
• Do NERC-ARF supply software to process the LiDAR data?
• Do NERC-ARF generate a DTM/DSM from LiDAR data?

Digital Camera Data

• How can I orthorectify RCD imagery?
• What is the content of the delivered event file?

Data Access

• How do I download delivered NERC-ARF data via FTP?
• How do I access the NERC-ARF data archive?
• How do I acknowledge NERC-ARF data in presentations/publications?

Datums and Projections

• If I load my NERC-ARF data with a GPS dataset in a GIS, they don't match. Why not? Otherwise known as, why is British National Grid projection not where it should be, and what is OSTN02?
• What is the difference between an ellipsoid, a geoid, a datum and a projection?

Older data

Azgcorr

PLEASE NOTE THAT AZGCORR IS NO LONGER BEING SUPPORTED AFTER 10 MAY 2015

• When I geocorrect data, Azgcorr stops and complains that the flightline has a turn in it - how can I process my data?
• Is there any way to speed up geocorrecting my data or to reduce the file size of the geocorrected files?
• Why are my geocorrected files much bigger than my level 1 files?
• Why are my geocorrected files upside down? Do I need to manually rotate images to make north "up"?
• Why do my geocorrected Eagle/Hawk files have unexpectedly red/green/blue/yellow pixels?
• My azgcorr has expired, where can I get a new one?
• What is the azgcorr ASCII DEM format?
• Why does azgcorr say "DEM does not enclose the image" and then stop, and how do I fix it?
• My image data is in a .bil file not an HDF, how do I geocorrect it with azgcorr?