[gdal-dev] working with AVIRIS data

[Dylan Beaudette]

On Monday 06 July 2009, Frank Warmerdam wrote:
> Dylan Beaudette wrote:
> > Hi,
> >
> >
> > Does anyone on the list know how to either convert or extract data as
> > delivered in the "free data" section [1] of the AVIRIS home page? I
> > have tried working with the "radiance" data, which when uncompressed
> > comes with several ".img" files-- however my copy of GDAL (1.7) does not
> > know what to make of it.
>
> Dylan,
>
> I downloaded  the cuprite radiance data and the readme says:
>
>
> *.img      CALIBRATED AVIRIS RADIANCE (IMAGE) DATA
>
> Contents:   AVIRIS calibrated radiance multipled by the gain and stored as
>              16-bit integers.
> File type:  BINARY 16-bit signed integer IEEE.
> Units:      gain times (microwatts per centimeter_squared per nanometer per
>              steradian).
> Format:     Band interleaved by pixel (channel, sample, line) with
> dimensions (224, 614, 512).  The last scene may be less than 512.  To
> calculate the number of lines divide the file size by 275,072 bytes per
> line.
>
> So it is a normal bigendian signed 16bit integer pixel interleaved dataset
> with a width of 614, a length of 512 and 224 bands.
>
> Based on the VRT tutorial at http://www.gdal.org/gdal_vrttut.html I wrote
> a .vrt file that allows access to the first band.
>
> <VRTDataset rasterXSize="614" rasterYSize="512">
>    <VRTRasterBand dataType="Int16" band="1" subClass="VRTRawRasterBand">
>      <SourceFilename
> relativetoVRT="1">f970619t01p02_r02_sc01.c.img</SourceFilename>
>      <ImageOffset>0</ImageOffset>
>      <PixelOffset>448</PixelOffset>
>      <LineOffset>275072</LineOffset>
>      <ByteOrder>MSB</ByteOrder>
>    </VRTRasterBand>
> </VRTDataset>
>
> gdalinfo -mm sc01.vrt
> Driver: VRT/Virtual Raster
> Files: sc01.vrt
> Size is 614, 512
> Coordinate System is `'
> Corner Coordinates:
> Upper Left  (    0.0,    0.0)
> Lower Left  (    0.0,  512.0)
> Upper Right (  614.0,    0.0)
> Lower Right (  614.0,  512.0)
> Center      (  307.0,  256.0)
> Band 1 Block=614x1 Type=Int16, ColorInterp=Undefined
>      Computed Min/Max=686.000,1381.000
>
> To support more bands just add additional copies of the VRTRasterBand
> section changing the band#, and adding two to the ImageOffset each time.
> eg.
>
> <VRTDataset rasterXSize="614" rasterYSize="512">
>    <VRTRasterBand dataType="Int16" band="1" subClass="VRTRawRasterBand">
>      <SourceFilename
> relativetoVRT="1">f970619t01p02_r02_sc01.c.img</SourceFilename>
>      <ImageOffset>0</ImageOffset>
>      <PixelOffset>448</PixelOffset>
>      <LineOffset>275072</LineOffset>
>      <ByteOrder>MSB</ByteOrder>
>    </VRTRasterBand>
>    <VRTRasterBand dataType="Int16" band="2" subClass="VRTRawRasterBand">
>      <SourceFilename
> relativetoVRT="1">f970619t01p02_r02_sc01.c.img</SourceFilename>
>      <ImageOffset>2</ImageOffset>
>      <PixelOffset>448</PixelOffset>
>      <LineOffset>275072</LineOffset>
>      <ByteOrder>MSB</ByteOrder>
>    </VRTRasterBand>
> </VRTDataset>
>
> You might want to write a small script to create this for 224 bands.
> Note the SourceFilename element - update this for other cubes.
>
> The same approach should work for the reflectance cubes (.rfl) if you
> are interested in them.
>
> Best regards,

Thanks Frank. This works well. Now I need to figure out how to apply the 
geo-rectification / distortion corrections from the .nav files... Some ideas 
here: ftp://popo.jpl.nasa.gov/pub/docs/workshops/99_docs/7.pdf

Cheers,
Dylan

-- 
Dylan Beaudette
Soil Resource Laboratory
http://casoilresource.lawr.ucdavis.edu/
University of California at Davis
530.754.7341