= Airborne Processing Library - Quick Start =

This is a short guide aimed at getting users geocorrecting their data straight away. For more in depth information please refer to the APL mapping user guide pdf.

== Creating an IGM file ==

An IGM file is a file that contains per-pixel latitude, longitude and height information, and relates directly to the level 1 file. Using the data contained in an ARSF delivery this can be done using the following command for an Eagle image, where the level 1 data file is named {{{flightline1.bil}}} and the output IGM file will be called {{{flightline1.igm}}}. The DEM used is the ASTER DEM as provided with the hyperspectral delivery.

{{{
aplcorr -lev1file flightlines/level1b/flightline1.bil -igmfile my_output/flightline1.igm -vvfile sensor_FOV_vectors/eagle_fov_fullccd_vectors.bil -navfile flightlines/navigation/flightline1_nav_post_processed.bil -dem dem/GB11_00-ASTER.dem
}}}

We now have per-pixel longitude and latitude values for the level 1 data of file {{{flightline1.bil}}}. But say we want to map the data to a different coordinate system. For this we need to re-project the IGM data.

== Reprojection from Geographic Latitude / Longitude ==

Reprojection is done in APL using the apltran software. This uses the open source PROJ libraries for performing the reprojection. There are 2 projections that have quick keywords set up in apltran; Ordnance Survey National Grid (OSTN02) and WGS84 Universal Transverse Mercator (UTM). To reproject {{{flightline1.igm}}} into UTM Zone 31 we could do the following:

{{{
apltran -inproj latlong WGS84 -igm my_output/flightline1.igm -output my_output/flightline1_utm31.igm -outproj utm_wgs84N 31
}}}