[postgis-users] defining new EPSG codes in spatial_ref_sys (was: equal area projection)

[Seb]

Hi,

AFAICT, whenever we deal with a local projection (one that's not already
listed as an "official" EPSG code) we have to insert a new row in the
spatial_ref_sys table to define a projection that can later be used to
reproject data.  But this means we need to invent a new EPSG code for
our particular area.  How do we go about that without creating a big
mess of conflicting codes whenever a new EPSG file comes up, or during
later upgrades of postgis or proj4?  Thanks.


Seb





On Tue, 17 Mar 2009 13:22:06 +0000,
mark balman <mark.balman at gmail.com> wrote:

> Hi Mark, thanks for your help:   At the moment I am using the
> following setup at work (I will install to the latest and greatest
> versions when I can park my current project)   PostgeSQL 8.2.5 with   
> "POSTGIS="1.3.1" GEOS="3.0.0rc4-CAPI-1.3.3" PROJ="Rel. 4.5.0, 22 Oct
> 2006" USE_STATS"   I have finally managed to get Mollweide into
> postgis and its working fine, I just need to reproject and upload 20+
> shapefiles now..    Once again, many thanks for the assistance!    ATB
>   Mark

> On Tue, Mar 17, 2009 at 9:54 AM, Mark Cave-Ayland <mark.cave-ayland at siriusit.co.uk> wrote:

    mark balman wrote:

        Hi all
>          I am trying to add a new equal area projection into postgis
> (behrmann and/or Robinson). I am struggling to get this to work.  From
> the "spatialreference.org <http://spatialreference.org>" website I
> uploaded the following into postgis:

>           INSERT into spatial_ref_sys (srid, auth_name, auth_srid,
> proj4text, srtext) values ( 954017, 'esri', 54017, '', 'PROJCS
> ["World_Behrmann",GEOGCS["GCS_WGS_1984",DATUM["WGS_1984",SPHEROID["WGS_1984",6378137,298.257223563]],PRIMEM["Greenwich",0],UNIT
> ["Degree",0.017453292519943295]],PROJECTION["Behrmann"],PARAMETER["False_Easting",0],PARAMETER["False_Northing",0],PARAMETER
> ["Central_Meridian",0],UNIT["Meter",1],AUTHORITY["EPSG","54017"]]');
>  After this I add some data in Behrmann projection using shp2pgsql,
> but trying a transform query such as  select
> AsText(transform(GeomFromText('Point(-75 10)',4326),954017))  does not
> work and crashes postgis.   I really need to get a global equal area
> projection to work for my project (have been using Plate Carree, but
> obviosly not good for performing area intersects) and would be
> grateful for any pointers on how to do this.   Many thanks  Mark

>     Hi Mark,

>     The SRTEXT parameter is actually not used for PROJ.4
> transformations - it's the proj4text field which is the important part
> and it appears it's blank in your SQL above. If you can find the
> equivalent PROJ.4 description, you should be fine.

>     BTW I'm quite surprised that PROJ.4 crashes with an empty
> proj4text - which version of PostGIS are you using?

>     ATB,

>     Mark.

>     -- Mark Cave-Ayland - Senior Technical Architect PostgreSQL -
> PostGIS Sirius Corporation plc - control through freedom
> http://www.siriusit.co.uk t: +44 870 608 0063
> _______________________________________________ postgis-users mailing
> list postgis-users at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users

> _______________________________________________ postgis-users mailing
> list postgis-users at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users



Cheers,

-- 
Seb