[gdal-dev] Python gdal -- Class or function equivalent to `gdaltransform'

[Jonathan Sawyer]

Frank (and all):

Thanks for the information. Using this link:

http://svn.osgeo.org/gdal/trunk/gdal/swig/python/samples/tolatlong.py

I was able to figure out how to transform points from one EPSG coordinate
system to another using Python. Here's how:

#transform()
def transform(i_srs, o_srs, lon, lat):
    # i_srs looks like "EPSG:4326"
    # o_srs looks like "EPSG:3338"

    from osgeo import osr

    i_num = int(i_srs.split(':')[1]) #obtain the EPSG number
    o_num = int(o_srs.split(':')[1]) #obtain the EPSG number

    srs_in = osr.SpatialReference() #create an input Spatial Reference
    srs_in.ImportFromEPSG(i_num) #import from EPSG:4326

    srs_out = osr.SpatialReference() #create an output Spatial Reference
    srs_out.ImportFromEPSG(o_num) #import from EPSG:3338

    ct = osr.CoordinateTransformation(srs_in, srs_out)
#CoordinateTransformation object from EPSG:4326 to EPSG:3338
    (X, Y, height) = ct.TransformPoint(float(lon), float(lat)) #Calculate
our transformed points

    return (X, Y, height)
#the returned values give exactly what is expected as per my previous email
#end of script

Thanks again everyone!

Jon

On Fri, Aug 21, 2009 at 6:03 PM, Frank Warmerdam <warmerdam at pobox.com>wrote:

> Jonathan Sawyer wrote:
>
>> Good evening developers,
>>
>> I am very new to GDAL, so please bear with me.
>>
>> What function/class/module do I need to look at to perform coordinate
>> transformation, in Python?
>>
>> Or better yet, can anyone point me to good online docs to learn how the
>> Python bindings are used in gdal?
>>
>> FYI: I am looking for the equivalent to this command line example:
>>
>> $ gdaltransform -s_srs EPSG:4326 -t_srs EPSG:3338
>> -146.673599867, 64.7163624865
>> 348408.577415968 1658661.40355536 0
>>
>> Have a good weekend, and thanks for your help.
>>
>
> Jonathan,
>
> There are some pointers to sample python scripts at:
>
>  http://trac.osgeo.org/gdal/wiki/GdalOgrInPython
>
> The tolatlong.py script has some example script for transforming
> points:
>
>  http://svn.osgeo.org/gdal/trunk/gdal/swig/python/samples/tolatlong.py
>
> Good luck,
> --
>
> ---------------------------------------+--------------------------------------
> I set the clouds in motion - turn up   | Frank Warmerdam,
> warmerdam at pobox.com
> light and sound - activate the windows | http://pobox.com/~warmerdam<http://pobox.com/%7Ewarmerdam>
> and watch the world go round - Rush    | Geospatial Programmer for Rent
>
>


-- 
Jonathan Sawyer
Geographic Information Network of Alaska (GINA)
University of Alaska Fairbanks
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