[gdal-dev] ENVI Rotation Bug Fix

[Damian Dixon]

Hi Taylor,

I'm just lurking on the mailing list myself.

I had a look at the code changes, as this is one of the formats I'm
interested in, and one point springs out at me:

const double PI = atan(1.0) * 4;

I find this line potentially a confusing way to define PI, particularly
when you combine it with (PI/180) later.

Personally I would use M_PI.

Regards
Damian



On 27 February 2017 at 11:55, Taylor Alexander Brown <
browtayl at oregonstate.edu> wrote:

> 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
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