[gdal-dev] gdal.AutoCreateWarpedVRT returning different results than osr.CoordinateTransformation

[Etienne Tourigny]

Billy,

You might consider creating a warped image with a larger pixel size (a
multiple of your real target size, say 3000m) to calculate the
"correct" extents and then throwing it away.

Etienne

On Sat, May 5, 2012 at 6:22 PM, Billy Newman <newmanw10 at gmail.com> wrote:
> Still very confused.
>
> I have a tiff file.  I want to get the metadata for that tiff but in
> EPSG:4326, without actually warping the image.  I can use
> CoordinateTransformation to do this, but again it gives me different results
> than gdalwarp.
>
> I will use gdalwarp later (realtime) to serve out an image.  But if the
> metadata I store (from CoordinateTransformation) is different than the
> metadata when I warp I will run into problems.
>
> gdalwarp gives something like minLon = 30.300001234, but
> CoordinateTransformation gives minLon = 30.29988787.  I want to gdalwarp
> number but without actually warping the entire image.
>
> I am not sure what .vrt file you are talking about.
>
> Thanks again
>
>
> On Sat, May 5, 2012 at 3:15 PM, Frank Warmerdam <warmerdam at pobox.com> wrote:
>>
>> On 12-05-05 01:19 PM, Billy Newman wrote:
>>>
>>> Can you think of a way that I can get the same metadata as gdalwarp would
>>> give
>>> for a warped image without actually warping the image?
>>
>>
>> Billy,
>>
>> Just open the .vrt and read the corners (that is compute them from the
>> size and geotransform).  There will not be any actual warping done just
>> to get this metadata from the .vrt but you will get the result
>> representative of the reprojected image.
>>
>>
>> Best regards,
>>
>> --
>>
>> ---------------------------------------+--------------------------------------
>> I set the clouds in motion - turn up   | Frank Warmerdam,
>> warmerdam at pobox.com
>> light and sound - activate the windows | http://home.gdal.org/warmerda
>> and watch the world go round - Rush    | Geospatial Software Developer
>>
>
>
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