[postgis-devel] PostGIS Raster problem

Jorge Arévalo jorge.arevalo at deimos-space.com
Thu Oct 20 01:05:19 PDT 2011


I think it may be a confussion here. If you are using the ST_Metadata
function, you're NOT using GDAL PostGIS Raster driver. The driver is
used to read raster data from database without using the SQL API. For
example, with gdalinfo, or gdal_translate.

Anyway, which GDAL version are you using?

On Wed, Oct 19, 2011 at 10:00 PM, David B�langer <belanger_david at live.ca> wrote:
> Thank you ! I'm using the revision r7616. I will use the current revision.
>
> David
>
>> Date: Wed, 19 Oct 2011 12:36:46 -0700
>> From: dustymugs at gmail.com
>> To: postgis-devel at postgis.refractions.net
>> Subject: Re: [postgis-devel] PostGIS Raster problem
>>
>> 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.
>>
>> -bborie
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>
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Jorge Arévalo
Internet & Mobility Division, DEIMOS
jorge.arevalo at deimos-space.com
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