[gdal-dev] gdal_grid - VRT - flipped image

[Even Rouault]

Le dimanche 16 juin 2013 22:19:21, Pierric a écrit :
> Hello,
> 
> By using the following commands, it creates a raster which is opened and
> shown correctly in GIS software but it is displaid upside down in an image
> viewer or internet browser. ( gdalinfo gives  Upper Right (  11.0000000, 
> 10.0000000) and Lower Right (  11.0000000,  70.0000000)  which shows image
> is upside down somehow )
> 
> Could you please help me to understand why ?  

Well, this is the behaviour of the utility that puts a correct, but unusual 
georeferencing. You can flip the image back to normal convention by using 
"gdalwarp src.tif out.tif" where src.tif if the output of gdal_grid.

> 
> I use GDAL_grid to convert a list of coordinates into a raster
> (interpolated).
> 
> - VRT file I use is :
> 
> <OGRVRTDataSource>
>     <OGRVRTLayer name="lonlat">
>         <SrcDataSource>lonlat.csv</SrcDataSource>
>     <GeometryType>wkbPoint</GeometryType>
>     <GeometryField encoding="PointFromColumns" x="longitude" y="latitude"
> z="ssha"/> </OGRVRTLayer>
> </OGRVRTDataSource>
> 
> - Command is :
> > gdal_grid -a invdist:power=3.0:smoothing=0.0: -zfield "ssha" -outsize 20
> > 10 -ot Int16  -a_srs EPSG:4326 -of GTiff -l lonlat lonlat.vrt A.tiff
> > --config GDAL_NUM_THREADS ALL_CPUS
> >
> >  gdalinfo A.tif
> 
> Size is 20, 10
> Coordinate System is:
> GEOGCS["WGS 84",
>     DATUM["WGS_1984",
>         SPHEROID["WGS 84",6378137,298.257223563,
>             AUTHORITY["EPSG","7030"]],
>         AUTHORITY["EPSG","6326"]],
>     PRIMEM["Greenwich",0],
>     UNIT["degree",0.0174532925199433],
>     AUTHORITY["EPSG","4326"]]
> Origin = (-80.000000000000000,10.000000000000000)
> Pixel Size = (4.550000000000000,6.000000000000000)
> Metadata:
>   AREA_OR_POINT=Area
> Image Structure Metadata:
>   INTERLEAVE=BAND
> Corner Coordinates:
> Upper Left  ( -80.0000000,  10.0000000)
> Lower Left  ( -80.0000000,  70.0000000)
> Upper Right (  11.0000000,  10.0000000)
> Lower Right (  11.0000000,  70.0000000)
> Center      ( -34.5000000,  40.0000000)
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