Basic azgcorr usage

Azgcorr is a command line driven geocorrection software package that can be used to create level-3 data from ARSF delivered level-1 data from the Eagle, Hawk, ATM and CASI instruments. Azgcorr is used to geocorrect data collected prior to 2011. If you have ARSF data that was collected during or after 2011 then you will need to use APL to process your data.

Compulsory arguments

• -1 <filename> This is used to specify the level-1 HDF file which you wish to geocorrect
• -3 <filename> This is used to specify the level-3 HDF file name that will be output from azgcorr
• -v This is not strictly compulsory but tells azgcorr to use verbose output. This is useful if you need to get in touch with us about an issue as it will give the developer more information how to solve this issue.

Some widely-used options

The following are the widely used options. For more information on these and other options please run azgcorr -help

Digital elevation model

Note that when using a DEM it should be in the same projection as the required level-3 output.

• -eh <filename> This is used to specify an ASCII DEM with the format as described here. If a DEM was delivered from ARSF (pre-2011) then this will be the format of the DEM, and is the format we recommended when using azgcorr.

• -es <filename> | NO This is used to specify whether to use a geoid-spheroid separation file. If the DEM has heights relative to the WGS84 spheroid then no geoid-spheroid shift is required (use -es NO). Else a suitable file (see here? to download) should be given unless using the -mUK99 projection (see below).

Output projection

• -mTMw CM This is the ARSF recommended map projection to get UTM data referenced to the WGS84 spheroid. You should replace CM with the central meridian of the UTM zone that you wish to map to, e.g. if you want to map to zone 31 you would replace CM with 3

• -mUK99 <filename> This is used to map data into the Ordnance Survey National Grid projection (OSTN02). You need to pass it a file that describes the OSTN02 projection (see here? to download). Note that you do NOT need to specify a geoid-spheroid shift when using this projection.

Pixel size

• -p X Y This is used to specify the output level-3 pixel size. e.g. -p 2 2 will output the data to square pixels of size 2m.

Band selection to map

• -bl LIST -1 This is used to specify a list of bands that you wish to map, note the trailing -1 which tells azgcorr that the list has finished. You should replace LIST with the space separated list of bands to map, e.g. -bl 100 50 45 -1 will map bands 100, 50 and 45.

Some example command lines

The following are example command lines that show possible usage.

• Map the bands 30, 15 and 7 from the file lev1.hdf to 2m pixels storing in a file called lev3.hdf. Use the OSTN02 transformation to get data in Ordnance Survey National Grid projection and use elevation data from my_ascii.dem.

azgcorr -v -mUK99 osgb02.cgrf -bl 30 15 7 -1 -p 2.0 2.0 -1 lev1.hdf -3 lev3.hdf -eh my_ascii.dem

• Map bands 100, 110, 120 and 130 from level1_data.hdf to WGS84 UTM zone 29 using 4m pixel size. Use elevation data, which is referenced to WGS84 spheroid, from the DEM named my_ascii_data.dem.

azgcorr -v -mTMw -9 -bl 100 110 120 130 -1 -p 4.0 4.0 -1 level1_data.hdf -3 level3_data.hdf -eh my_ascii_data.dem -es NO