Problem with conversion from GeoTIFF to ENVI

[mariocavicchi]

I have converted a GeoTIFF image with gdal_translate to ENVI and i have obtained a header file without rotation information, and it's wrong, instead ENVI program make a header file right.

I made a simple program that uses function GDALCreateCopy, but the result is equal. I can send original image if it may help.

I use this version og GDAL:

$ gdal_translate --version
GDAL 1.5dev, released 2007/04/01

[warmerdam]

Chris,

Could you confirm this problem (in trunk)? If the problem is confirmed as still present, we can either turn it over to Donnie Marino (dmarino) (who maintains this driver) or you could fix it with some support from him.

If the changes to support it are not too disruptive we should try to retrofit to 1.5 branch, otherwise fix only in trunk.

[Jukka Rahkonen]

Some findings: Document ​http://www.exelisvis.com/docs/ENVIHeaderFiles.html does not list "rotation" as an info item of ENVI header file in the "map info" section but that must be an error in the documentation. A page linked from the header file section ​http://www.exelisvis.com/docs/enteroptionalheaderinformation.html#Enter2 describes the usage of rotation as "If North is not up in the image, enter a rotation angle in degrees in the Map Rotation field. Measure the angle in a clockwise direction where zero degrees is straight up."

For me this ticket feels a bit like invalid because it handles the case when GDAL is used for converting tiff file into ENVI. I do not know how where the original tiff file could hold the info about rotation and based on the latter document above even in ENVI user interface user must feel the rotation parameter by hand. It could be suitable for a case when original GeoTIFF is georeferenced with GCPs in such a way that rotating the image would be enough and no warping would be needed which feels like a special case.

There is a perhaps more critical issue with reading ENVI images with rotation. See ​http://lists.osgeo.org/pipermail/gdal-dev/2013-January/035146.html and a ticket that is closed as invalid but which probably is still valid http://trac.osgeo.org/gdal/ticket/4342.

[Even Rouault]

GDAL could use the rotation to set the proprer values in the gt[1], gt[2], gt[4] and gt[5] terms of the geotransform matrix. And reciprocaly if those terms are rotational only, the rotation keyword could be written.

[Even Rouault]

Removing obsolete milestone

[Even Rouault]

In 37506:

ENVI: add read/write support for rotated geotransform (read support from Taylor Alexander Brown github #197, write support by myself, fixes #1778)