[gdal-dev] gdal_translate -a_srs

[Greg Coats]

Frank, Yes! Thank you. Greg

On Jul 5, 2010, at 7:25 PM, Frank Warmerdam wrote:

> Greg Coats wrote:
>> Following Frank's suggestion, and in accordance with the web page GDAL Utilities http://www.gdal.org/gdal_utilities.html Creating New Files
>> I issued these GDAL commands
>> $ gdal_translate --version
>> GDAL 1.7.2, released 2010/04/23
>> $ gdal_translate -of GTiff -ot Uint16 -a_srs NAD83_UTM18N.wkt in.tif out.tif
>> $ gdal_translate -of GTiff -ot Uint16 -a_srs EPSG:26918       in.tif out.tif
>> The two out.tif files created are identical.
>> gdalinfo shows that out.tif has the expected values for PROJCS through AUTHORITY, including
>> UNIT["metre",1,
>> but gdalinfo shows out.tif still has latitude longitude values for Origin and Pixel Size  Origin = (-78.000555555559998,40.000555555555515)
>> Pixel Size = (0.000092592592593,-0.000092592592593)
>> rather than the expected Origin and Pixel Size values for NAD 1983, UTM Zone 18N of about
>> Origin = (271500.000000000000000,4335000.000000000000000)
>> Pixel Size = (38.385826771653548,-38.385826771653548)
>> This Origin and Pixel Size difference prevents out.tif from being displayed by Qgis along with the original NAD 1983 UTM Zone 18N .tif. It is though the gdal_translate -a_srs process is only partially complete? What additional step is necessary so that out.tif has Origin and Pixel Size values in UTM, rather than lat/long?
> 
> Greg.
> 
> The -a_srs switch assigns a new coordinate system.  It does not reproject
> the image.  I think you want to use gdalwarp like:
> 
>  gdalwarp -t_srs EPSG:26918 in.tif out.tif
> 
> Best regards,
> -- 
> ---------------------------------------+--------------------------------------
> I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
> light and sound - activate the windows | http://pobox.com/~warmerdam
> and watch the world go round - Rush    | Geospatial Programmer for Rent
>