Frequently Asked Questions
This page is designed to complement the Help page. If you ask us one of the questions on this page, you're likely to get an answer copy/pasted from here. If you have read this answer and are still unclear, please mention that you've looked at this page when you contact us so that we don't just give you the same answer again.
- 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?
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?
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 is the file format for my ASCII LiDAR data files?
- How do I convert between LAS and ASCII file formats?
- Do the ARSF supply software to process the LiDAR data?
- Do the ARSF generate a DTM/DSM from LiDAR data?
RCD Camera deliveries
Level 1 Data
- 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?
Datums and Projections
- If I load my ARSF 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?