[FWTools] Extract to binary with meta, manipulate, then project

Simon Hook simon.j.hook at jpl.nasa.gov
Sun Feb 4 15:37:53 EST 2007

Hi Frank,

(see embedded comments)

Frank Warmerdam wrote:
> Simon Hook wrote:
>> Hi Frank,
>> The processing I do will likely add or take away bands but the x and 
>> y dimensions of the image will stay the same. Assuming I can edit the 
>> .aux file (i.e. it is ascii rather than binary) that should work.
> Simon,
> The PAux driver's .aux file is a simple ascii file.
> > Does the
>> aux just use the 4 corners? I am not sure if you know this but ASTER 
>> files contain two arrays (1 lat, 1 lon), with points throughout the 
>> scene, that should be expanded to produce a lat/lon for each pixel. 
>> If you use the 4 corners, there will be some error because pixel 
>> spacing varies across the scene. Several programs ignore these 
>> arrays, e.g. ENVI. Also can you extract all the ASTER products, not 
>> just the 1B (I want to do some work with the emissivity product).
> GDAL has a mechanism to keep track of lat/lon bands per:
>   http://www.gdal.org/rfc4_geolocate.html
> This *should* exist for 1B ASTER products, so you can extract the lat and
> lon as distinct files if you want.  But, the gdalwarp program does not
> currently support this kind of geolocation array, so you can't ultimately
> use them to geocode your image unless you have something else to do the
> actual work.
How do I extract these lat/lon arrays, I am lost as to what utility to 
use, and how to use it. Note the embedded lat/lon arrays are a subset, 
they are not a 1 to 1 match. This is also true with MODIS.

> Note that metadata does not get written to .aux files, so the correct
> subdataset identify for geolocation arrays will only be evident in the
> gdalinfo report, not the .aux file.
> The GDAL HDF4 driver attempt to be broadly useful for a variety of
> HDF4 format products, and it should be useful for a variety of ASTER
> product levels.  However, the extraction quality of geolocation, and 
> metadata
> may vary.
> Best regards,

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