[postgis-users] ST_Difference

[Richard Heimann [C]]

Thanks for your response W. I should have posted the sql query earlier.
Anyway...its below.

My goal is to drop all features (points) that fall within my polygon. In
this case, I have ship track data and want to filter it with world country
buffers. 

World2_12nm - my world country 12nm buffered polygon
Pandatestdata - track data (point)
Panda_diff2 - new table


CREATE TABLE panda_diff2 AS
SELECT AsText(Difference(world2_12nm.the_geom, pandatestdata.the_geom)) FROM
world2_12nm, pandatestdata

Also attached are the astext versions of my data as well as a csv of the
output from the above sql. Please debunk the mystery...

Thanks again
Rich

-----Original Message-----
From: Webb Sprague [mailto:webb.sprague at gmail.com] 
Sent: Wednesday, October 24, 2007 12:00 PM
To: Richard.Heimann at nrl.navy.mil; PostGIS Users Discussion
Subject: Re: [postgis-users] ST_Difference

You might get more useful help if you post an "astext()" version of
your data, the query, the result, and  a *desired* result.

I know the difference functions can be tricky and are sometiimes
defined in ways you might not expect.

Thx
W

On 10/24/07, Richard Heimann [C] <heimann at ait.nrl.navy.mil> wrote:
>
>
>
>
> All,
>
>
>
> I would appreciate help in constructing an SQL statement that performs a
> difference function on two datasets. My intersect function works but
cannot
> work out the kinks with st_difference. Thanks for your help.Im new to
> Postgis.
>
>
>
> Rich
>
>
>
>
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