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Last Post 28 Aug 2004 06:00 PM by  anon
ASTER HDFEOS file reading geolocation
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anon



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28 Aug 2004 06:00 PM
    Hi, I use ENVI's EOS tools such as EOS_SW_OPEN() to deal with ASTER data. All went perfectly. I got the Swath and Fields and then the data array. Well, but I still need the geolocation information to export as Geotiff. However I canonly find lat and lon using the LonResult = EOS_SW_ReadField( SwathID, GeoArr(0), LonBuf ) function. I cannot find the projection,earth model, or resolution information! But if I use the envi_file_open routine to use the GUI to do the same thing, it comes with geolocation. So what is the thing that ENVI routine does to fetch the geoinfo that I cannot find out through EOS functions in IDL? Thanks a hundred times.

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    28 Aug 2004 06:00 PM
    In my ASTER data I use OK = eos_sw_readfield(swid, 'GeodeticLatitude', lats) OK = eos_sw_readfield(swid, 'Longitude', longs) to get arrays of latitudes and longitudes I get 11 element arrays which I assume map evenly across the image (10 intervals in between). I think lat-long may be how the image is referenced. Since it's satellite data I would assume WGS 84 as a geodetic datum. You could then choose an appropriate projection (e.g the apropriate UTM zone) and use 15 m for VNIR, 30 m for SWIR, and 90 m for TIR. As a related issue, I think ENVI has a bug in outputting GeoTIFF from HDF EOS - need to flip the signs on a couple of the affine coeff. Use listgeo and geotifcp to examine and fix.
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