[postgis-devel] PostGIS Raster problem

dustymugs dustymugs at gmail.com
Wed Oct 19 12:36:46 PDT 2011

On 10/19/2011 12:21 PM, David B�langer wrote:
> Hi,
> I use the GDAL driver to extract a raster from PostGIS 2.0  but I got bad results. The x and y of the upper left corner and the resolution are bad. It seems that these properties have been rounded. This problem has appeared since the summer version of PostGIS 2.0. I didn't have this problem before. I think the problem is in the ST_MetaData()  function  which is used by the GDAL driver. I know that this function was modified this summer. The others functions (eg. ST_ScaleX, ST_ScaleY, ST_UpperLeftX...) give good results.
> I have compared the result of the summer version of PostGIS  with the old version.
> The results:
> select ST_MetaData(rast)…:
> Old version of database: "(-71.7501041666667,45.5001041666667,1200,1200,0.000208333333333333, 0.000208333333333333,0,0,4269,1)"
> Database Since this summer: "(-71.750104,45.500104,1200,1200,0.000208, -0.000208,0,0,4269,1)"
> The result of the old version of the database is the truth.
> Does anyone know this problem and can you help me?
> Thanks !
> David 		 	   		

What revisions of PostGIS trunk are you using?  I rewrote the 
ST_Metadata function over the summer and had to tweak it some time 
afterwards due to how the values were getting rounded depending on how 
the C function returned (Datums vs. CStrings).

After digging through the logs, you'll want to be using r7638 
(7/14/2011) or more recent to ensure that your answers are correct.


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