That's what I thought ... my morning coffee hadn't kicked in yet :)
It still looks like PostGIS might benefit from a
ShiftCoordinates(linearring geometry) function to solve this particular
problem.
-- Kevin
On 10/22/2010 10:45 AM, David William Bitner wrote:
D-P simplification is not going to
D-P simplification is not going to modify your start/end points. For a bit
of reference on the Douglas-Peuker simplification algorithm, see
http://en.wikipedia.org/wiki/Ramer%E2%80%93Douglas%E2%80%93Peucker_algorithm
On Fri, Oct 22, 2010 at 11:13 AM, Kevin Neufeld wrote:
> I don't see any pdf pos
I don't see any pdf posted, but that's ok, I get the idea.
Isn't that interesting. To me, this looks like a robustness issue with
ST_Simplify. Here, the starting point of the polygon's exterior ring is
not on the corner.
select
st_astext(
st_simplify(
'POLYGON ((
25 300,
Hi Kevin,
Hopefully the attached (hopefully) PDF will help to show what i mean.
In producing the PDF i think i can see why the issue happens. It seems that
the start and end point of the polygon geometery are the node i was hoping
might be removed during the simplify process.
Not sure if there
Hi Andy,
Can you post a small example?
-- Kevin
On 10/21/2010 10:02 AM, lplateandy wrote:
Hi,
I have, in the simplest example, a square polygon of 1 by 1 kilometer size
with nodes every 25 meters.
I can use ST_Simplify (the_geom,5) to remove most of the points.
However, for some reason i en
Hi,
I have, in the simplest example, a square polygon of 1 by 1 kilometer size
with nodes every 25 meters.
I can use ST_Simplify (the_geom,5) to remove most of the points.
However, for some reason i end up with the four corner nodes and a fifth
node 25m clockwise from the top left corner.
In i
Hi,
yes, the Simplify() command is an implementation of the Douglas-Poiker
algorithm. This algorithm is direction dependent, which is a problem in
Postgis, which stores edges in polygon mosaics twice.
I've just recently discussed this issue with a colleague, who is
currently looking into imp
A question regarding the function ST_Simplify:
I have a postgis layer of watershed polygons that I would like to
simplify, yet while keeping all shared edges. In other words, I'd
like to remove vertices along shared boundaries without creating gaps
between adjacent polygons. I'm no expert i
