[gdal-dev] ENVI Rotation Bug Fix

[Taylor Alexander Brown]

Greetings GDAL Community,

I am developing an application [0] to process georeferenced raster
hyperspectral imagery in ENVI format from NASA's Airborne
Visual/Infrared Imaging Spectrometer (AVIRIS) [1].

The `map info` section of the header files contain an undocumented [2]
rotation field which is currently ignored by GDAL. As a result, the
image is rotated incorrectly when I process it with `gdalwarp` or the
GDAL Python API. Furthermore, the image is scaled incorrectly when I try
to override the geotransform.

I documented my experiences on the GIS Stack Exchange [3]. It has
previously been described on the GDAL mailing list [4] and bug tracker
[5]. I believe this issue also affects ASTER imagery [6][7].

I have implemented a fix based off of branch `tags/2.1.3` and shared my
code on GitHub [8]. It reads the `units` and `rotation` parameter from
the `map info` section and uses these to calculate the geotransform. The
scaling was off because the code expected the `units` parameter to be
the last element in the list, when in my case it was the second to last.
You can verify this behavior with the single-band image I have been
using for testing [9].

You are welcome to evaluate my code and contribute it back to the
library. I am a novice at both GDAL and GIS, so there may well be
problems. I would be willing to submit a pull request against your
GitHub mirror if desired.


Peace,

Taylor Alexander Brown


[0] https://github.com/capstone-coal/pycoal
[1] https://aviris.jpl.nasa.gov/
[2] http://www.harrisgeospatial.com/docs/enviheaderfiles.html
[3]
http://gis.stackexchange.com/questions/229952/rotate-envi-hyperspectral-imagery-with-gdal
[4] https://lists.osgeo.org/pipermail/gdal-dev/2013-January/035146.html
[5] https://trac.osgeo.org/gdal/ticket/1778
[6] http://yceo.yale.edu/opening-aster-files-envi
[7] http://yceo.yale.edu/faq-page#t2n504
[8]
https://github.com/OSGeo/gdal/compare/tags/2.1.3...browtayl:fix-envi-rotation?expand=1
[9] https://drive.google.com/open?id=0BxysdOuBmaIGalY5dVhCa1Y5M0k