[postgis-users] Some questions concerning postgis

Paragon Corporation lr at pcorp.us
Tue Jan 27 00:21:28 PST 2009


Try OpenJump.  Its great for ad hoc PostGIS queries.

We have a brief primer on it here.


-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of
Sent: Tuesday, January 27, 2009 2:12 AM
To: PostGIS Users Discussion
Subject: Re: [postgis-users] Some questions concerning postgis

Hello Leo and Paul,

thanks for your answers. The data, I have here, consists of 5204 polygons,
each having a common border with some others (screenshot of the first half
attached). The data requires heavy generalization, because it is unnecessary
detailed - at least in terms of a planned web based vector map presentation
(GM, VE, OSM etc.). I guess, simply "Douglas-Peuker'ing" each polygon isn't
helpful, because splits and cavities may be produced by an algorithm, which
doesn't mind the semantical context of all the polygons. I've found
mapshaper.org (which isn't working with my data) and this
I could make the latter run, at least for the first step - the vertex
creation. Don't know, what results may arise, because it takes hours to
calculate the things, and I currently have no means to "visualize" the
results. What would you suggest for visualization? I know mapserver, but do
I really have to go this way in order to see the table based data?

I'm using SQL Server 2008 normally, there is a in-build viewer. Is something
similar available for PG?


Paul Ramsey schrieb:
> On Mon, Jan 26, 2009 at 3:54 PM, Paragon Corporation <lr at pcorp.us> wrote:
>> Though if you want to maintain borders I guess you would probably 
>> want to
>> 1)  convert your polygons to linestrings using ST_Boundary,
>> 2) dump out into edges and grouping by the gid
>> 3) Simplify and then repolygonize.
> It is hard. Kevin gave a recipe for it once though... perhaps he'll 
> wikify it this time...
> P
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