SRS Magic

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SRS Magic

Paul Ramsey
One of the constant requests to make postgis easier to use is SRID
detection. At this point GDAL has almost all the bits and pieces to do
SRID detection from PRJ inputs. That would be a nice feature to add.
On a similar note, we could start using SRTEXT entries to support
reprojection in cases where PROJ4TEXT entries are missing, though I
haven't heard too many complaints about that.

P
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Re: SRS Magic

Sandro Santilli-2
On Thu, Oct 29, 2015 at 09:23:14AM -0700, Paul Ramsey wrote:
> One of the constant requests to make postgis easier to use is SRID
> detection. At this point GDAL has almost all the bits and pieces to do
> SRID detection from PRJ inputs. That would be a nice feature to add.
> On a similar note, we could start using SRTEXT entries to support
> reprojection in cases where PROJ4TEXT entries are missing, though I
> haven't heard too many complaints about that.

Could the GDAL feature be available separated from the whole of GDAL ?
An srslib kind of thing ?

--strk;
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Re: SRS Magic

Paul Ramsey
It’s been talked about before (crslib, etc) but as with PostGIS, gutting ones project for the benefit of others is never an appealing notion, no matter how many others might benefit. So it hasn’t happened.


On October 29, 2015 at 10:13:32 AM, Sandro Santilli ([hidden email]) wrote:

On Thu, Oct 29, 2015 at 09:23:14AM -0700, Paul Ramsey wrote:
> One of the constant requests to make postgis easier to use is SRID
> detection. At this point GDAL has almost all the bits and pieces to do
> SRID detection from PRJ inputs. That would be a nice feature to add.
> On a similar note, we could start using SRTEXT entries to support
> reprojection in cases where PROJ4TEXT entries are missing, though I
> haven't heard too many complaints about that.

Could the GDAL feature be available separated from the whole of GDAL ?
An srslib kind of thing ?

--strk;
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Re: SRS Magic

Even Rouault-2
In reply to this post by Paul Ramsey
Le jeudi 29 octobre 2015 17:23:14, Paul Ramsey a écrit :
> One of the constant requests to make postgis easier to use is SRID
> detection. At this point GDAL has almost all the bits and pieces to do
> SRID detection from PRJ inputs.

Paul,

if by PRJ, you mean ESRI Shapefile .prj files whose WKT definition strips off the
EPSG code even when the WKT is derived from an EPSG definition, then indeed
there's some magic to add in GDAL to guess the EPSG code. There's a
AutoIdentifyEPSG() method (
http://www.gdal.org/classOGRSpatialReference.html#acb0373c83927bfd694048da6f79e33ea 
) but it is fairly limited.

Even

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Re: SRS Magic

Stefan Keller
Cool AutoIdentifyEPSG() method!

Sorry for creeping in for a related issue: But what is the correct
value for an undefined SRID: Is it 0 or -1 or both?

PostGIS changed from -1 to 0... I thought so far [1].
Until I found this [2] and this [3] which mention or refer to SRID value -1.

Then I looked at GeoPackage spec. [4] which uses both!
"The record with an srs_id of -1 SHALL be used for undefined Cartesian
coordinate reference systems. The record with an srs_id of 0 SHALL be
used for undefined geographic coordinate reference systems.".

What is the state in PostGIS?
Which is "more compliant" to ISO SQL/MM: PostGIS or GeoPackage spec.?

:Stefan


[1] PostGIS Ticket #286 "Change "no SRID" SRID to 0":
https://trac.osgeo.org/postgis/ticket/286
[2] PostGIS FAQ: http://postgis.org/documentation/manual-2.1SVN/PostGIS_FAQ.html
[3] PostGIS Docs: http://postgis.net/docs/using_postgis_dbmanagement.html
[4] GeoPackage Spec.: http://www.geopackage.org/spec/#spatial_ref_sys


2015-10-29 18:22 GMT+01:00 Even Rouault <[hidden email]>:

> Le jeudi 29 octobre 2015 17:23:14, Paul Ramsey a écrit :
>> One of the constant requests to make postgis easier to use is SRID
>> detection. At this point GDAL has almost all the bits and pieces to do
>> SRID detection from PRJ inputs.
>
> Paul,
>
> if by PRJ, you mean ESRI Shapefile .prj files whose WKT definition strips off the
> EPSG code even when the WKT is derived from an EPSG definition, then indeed
> there's some magic to add in GDAL to guess the EPSG code. There's a
> AutoIdentifyEPSG() method (
> http://www.gdal.org/classOGRSpatialReference.html#acb0373c83927bfd694048da6f79e33ea
> ) but it is fairly limited.
>
> Even
>
> --
> Spatialys - Geospatial professional services
> http://www.spatialys.com
> _______________________________________________
> postgis-devel mailing list
> [hidden email]
> http://lists.osgeo.org/mailman/listinfo/postgis-devel
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