[gdal-dev] New to list and question (UNCLASSIFIED)

[Jorge Arévalo]

Hi Jonathan,

On Tue, Feb 8, 2011 at 4:46 PM, Lefman, Jonathan ERDC-TEC-VA
<Jonathan.Lefman at usace.army.mil> wrote:
> Classification: UNCLASSIFIED
>
> Caveats: NONE
>
> Hi all,
>
> I joined this list today.  I have a question about using Python bindings
> with GDAL to get info from a geotiff.
>
> What are the functions that I need to obtain coordinate extents of raster
> data?  For example, if I have a rectangular area from Washington, DC with
> coordinates in UTM format, how would I determine the top-left and
> lower-right corners?  I was unable to find an example in the documentation.
>
> Here’s a snippet of my code of where I’m at:
>
> from osgeo import gdal
>
> gdaldata = gdal.Open(gtiff_filename)
>
> prj = gdaldata.GetProjection()
>
> trfm = gdaldata.GetGeoTransform()
>
> Thanks everyone,
>
> Jon
>
> Classification: UNCLASSIFIED
>
> Caveats: NONE
>
> _______________________________________________
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> gdal-dev at lists.osgeo.org
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>

Test this:

from osgeo import gdal

def calculate_geoxy(gt, xy):
    """Calculate georeferenced coordinate from given x and y"""
    xgeo = gt[0] + gt[1] * xy[0] + gt[2] * xy[1];
    ygeo = gt[3] + gt[4] * xy[0] + gt[5] * xy[1];

    return (xgeo, ygeo)

ds = gdal.Open(gtiff_filename)
prj = ds.GetProjection()
gt = tuple(list(ds.GetGeoTransform()))
dim = ( (0,0),(0,ds.RasterYSize),(ds.RasterXSize,0),(ds.RasterXSize,ds.RasterYSize)
)
ext = (calculate_geoxy(gt, dim[0]), calculate_geoxy(gt, dim[1]),
           calculate_geoxy(gt, dim[2]), calculate_geoxy(gt, dim[3]))


Best regards,

-- 
Jorge Arévalo
Internet & Mobilty Division, DEIMOS
jorge.arevalo at deimos-space.com
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