[postgis-users] Getting dimensions of polygon sides
robe.dnd at cityofboston.gov
Wed Jun 11 08:01:56 PDT 2008
I'm trying to similuate ArcGIS annotations. I guess ArcPad doesn't
support ArcGIS annotations according to what I have been told but can
support line strings and so forth.
Here is the the problem. I have a set of parcel polygon geometries.
I'm going to assume that each lines side is composed of 2 points and no
polygon has more than 1000 sides. I need to create a table that has a
separate row for each side with the length of that side as an attribute
I stupidly thought I could take the boundary and then figure out the
length of the boundary forgetting that this just gives me the perimeter.
So my second thought was that if I reconstitute points of the boundary
grouping 2 at a time - that would do the trick.
My query is still running so haven't looked to see what the final result
is. I'm wondering if someone has done something similar and if they
have an easier way.
Below is the query I am testing right now.
INSERT INTO assessing.parcdimstime_2008(pid, pid_year, the_geom)
SELECT b.pid, b.pid_year, ST_MakeLine(ST_PointN(the_boundary,n),
ST_PointN(the_boundary, n + 1)) As the_side
FROM (SELECT pid, pid_year, the_boundary,
ST_NumPoints(the_boundary) As nump
FROM (SELECT pid, pid_year, ST_Boundary(the_geom) As
WHERE pid_year = 2008) p) As b
CROSS JOIN generate_series(1, 1000) n
WHERE n < b.nump;
UPDATE assessing.parcdimstime_2008 SET sd_length = ST_Length(the_geom);
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