[postgis-devel] pgraster: st_resample error

[Bborie Park]

Disregard my last message.  I double-checked the scale-Y coming from
ST_Resample versus that of gdalwarp and everything matches.  The drift
is definitely coming from the projection string used in the warping.
I'll have to ask the GDAL ML if I can pass a proj4 string instead of a
WKT string.

-bborie

On Fri, Dec 23, 2011 at 8:01 AM, Bborie Park <dustymugs at gmail.com> wrote:
> I plan on posting there after I do some experimenting.  The 20KM north
> or south is probably coming from the plus or minus used for scale-Y.
> I believe GDAL defaults to a negative value for scale-Y while PostGIS
> Raster will use the scale-Y of the input raster.
>
> -bborie
>
> On Fri, Dec 23, 2011 at 7:58 AM, Tom van Tilburg
> <tom.van.tilburg at gmail.com> wrote:
>> Hi Bborie,
>>
>> thanks.
>> I keep an eye on the ticket but it's a bit beyond my abilities to understand
>> all of it ;-)
>>
>> My 2 cents however on Evens post:
>>
>> The errors in the amersfoort (28992) projecten have been known for a long
>> time, that's not what bothers me at the moment.
>>
>> From all the small errors in the google-mercator projections (I think there
>> are 4 around, all slightly different) I have never seen 20 km. error in the
>> offset. It more feels to me that numbers have been swapped instead of
>> miscalculated.
>> The fact that postgis moves it 20 km south while gdal_warp moves it 20 km
>> the opposite direction is also puzzling. What could that indicate?
>>
>> I'll keep an eye on the gdal list as well. Are you posting there?
>>
>> Cheers,
>>  Tom
>>
>>
>>
>> On 23-12-2011 16:38, Bborie Park wrote:
>>>
>>> Tom,
>>>
>>> When you have the chance, can you look at ticket #1402?
>>>
>>> http://trac.osgeo.org/postgis/ticket/1402
>>>
>>> Even from the GDAL project responded with a thorough explanation of
>>> what's causing the drift.  I'm still digesting his explanation and
>>> will see what can be done to improve the projection handling in
>>> PostGIS Raster.  Currently, we use the value in the "srtext" column of
>>> spatial_ref_sys, but it looks like we may have better luck using the
>>> "proj4text" column and have GDAL process it through their mechanisms.
>>>
>>> -bborie
>>>
>>>
>>
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