[FWTools] gdal_translate, -a_srs, -a_ullr, and Projections with Rotations [RESOLVED]

[Peter Willis]

Hello,

Thank you Even.
This is the correct solution. Everything is mapping to
the proper position now.

To summerize:

1.) use gdal_translate  with the -gcp option to define ground control 
points in the raw image.

2.) use gdalwarp on the new raw image, now with embedded control points,
to create the final mapped output geotiff.

Thank you for your help.

Peter


Even Rouault wrote:
> I've read very quickly what you want to do, so I might have not understood 
> well. But here are a few hints :
> * the spatial coordinates you give for each GCP must be consistant with the 
> projection (you can set it with -a_srs if needed).
> * You can't use -gcp and -a_ullr at the same time.
> * After adding GCPs with gdal_translate, you can use gdalwarp to apply to 
> rotation to the pixel data.
> 
> Le Wednesday 22 July 2009 19:59:28 Peter Willis, vous avez écrit :
>> Hello,
>>
>> Well, I tried with GCPs but no UTM geography is applied to
>> the output unless I supply the '-a_ullr' option. Using
>> -a_ullr causes the GCPs to be ignored and the same pixel
>> size calculation errors occur due to the rotation and
>> the actual bottom right coordinates with respect to the
>> upper left.
>>
>> gdal_translate appears to be calculating the pixel size
>> based on the UL and LR corners, which is normal. However,
>> with GCPs there should be more of a rotation/translation
>> applied to the geography.
>>
>> Perhaps an option to override the pixel size calculations
>> in each dimension should be added to the utility...
>>
>> Peter
>>
>> Peter Willis wrote:
>>> Hello,
>>>
>>> I just noticed the '-gcp' option for gdal_translate.
>>> It occurs to me that this should provide the required projection
>>> adjustments.
>>>
>>> Peter
>>>
>>> Peter Willis wrote:
>>>> Hello,
>>>>
>>>> I am applying geography to some UTM based images.
>>>> The images have a 1.9 degree rotation.
>>>>
>>>> Is there a way to assign a rotation to the projection
>>>> using gdal_translate?
>>>>
>>>> If not, is there a way to assign the rotation using
>>>> any other GDAL tools?
>>>>
>>>> Thanks
>>>>
>>>> Peter
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> 
> 
> 
> 
> 


-- 
Peter Willis

Remote Sensing Analyst, Programmer, Electronics Technician

ASL Borstad Remote Sensing Inc.

1986 Mills Road
Sidney, British Columbia, Canada V8L5Y3
Tel: 250-656-0177 extension 135