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Re: [udig-devel] World Mercator with postgis
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Hi Jody,
Thanks for the response.
I am having difficulty adding my own SRID, and getting uDig to recognize it. What I really want is to be able to support this in my own custom application, but for now, I am running uDig from Eclipse -- I don't know if that changes things.
This is what I've done: I created a geometry table in PostGIS, and set the SRID to 3395 (the SRID in PostGIS for "WGS 84 / World Mercator"). When I load the layer into uDig, the CRS is set to 4326. That didn't work.
Next, I created a geometry table in PostGIS, and set the SRID to 41001 (the SRID in uDig for "WGS84 / Simple Mercator" -- this is nearly the same, and would suit my purposes if it would work). When I load the layer into uDig, the CRS is set to 4326.
I assumed that the problem was that PostGIS and uDig had to have the same CRS in both their systems, so the SRID in the PostGIS spatial_ref_sys table matches the EPSG code in uDig's Coordinate System dialog. Sure enough, if I set the PostGIS spatial reference to something else (for my test, I used EPSG:4269), then when it loads into uDig, the CRS is set correctly.
Additionally, when I attempt to add the definition from PostGIS (the srtext from the spatial_ref_sys table) for 3395 into the Custom CRS box in uDig, I can press "Apply" and "OK" to my heart's content, but the dialog never closes, and I can't get out of the dialog without canceling.
Please advise,
David
On Wed, Feb 11, 2009 at 6:42 PM, Jody Garnett
<jody.garnett@xxxxxxxxx> wrote:
Mark Leslie is the postgis guy I know these days and he can confirm or deny what I say here :-)
You can add your own SRID codes to to PostGIS and define one th be generic cartesian 2D if you like. UDig will pick up this WKT definition and be fairly happy.
In uDig you click to change the projection; there are two tabs (one where you select the formal epsg definition from a list; and a second where you can type in your own WKT). You can also right lick on a layer and "force" a change of projection (if the data source is wrong for example - it does happen).
Mercator is supported in our referencing library so you should be able to proceed resonably well. Normally PostGIS SRID codes line up with the EPSG codes ...
Jody
David Zwarg wrote:
Hello,
I am wondering if there is a way to use the World Mercator projection in PostGIS in uDig. I am unable to use either the PostGIS (3395) or the uDig (41001) EPSG codes for world mercator in my PostGIS layer -- they both show up as Generic cartesian 2D. As soon as I attempt to add geometry and edit geometry, uDig goes into an endless loop of IllegalArgumentExceptions.
However, if I use an EPSG code that appears in BOTH postgis and uDig, it seems to work alright. If there was a way to represent Generic cartesian coordinates in PostGIS, that would be preferable, but -1 causes this same IllegalArgumentException spiral. Am I missing a general projection that would be more suitable?
Also, during this experiment, I was unable to create a custom CRS in the uDig map preferences, or by clicking on the button in the status bar. How do you create a custom CRS from a known WKT?
Thanks,
David
_______________________________________________
User-friendly Desktop Internet GIS (uDig)
http://udig.refractions.net
http://lists.refractions.net/mailman/listinfo/udig-devel
_______________________________________________
User-friendly Desktop Internet GIS (uDig)
http://udig.refractions.net
http://lists.refractions.net/mailman/listinfo/udig-devel
