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Results tagged with geometry
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user 960
(1) abstract geometry; (2) storing geographic data in projected coordinates; (3) a generic ESRI term for vector features; a class for "geometry" objects.
2
votes
modeling of spatial objects
('POLYGON((15 4, 19 3, 21 6, 24 2, 18 0, 14 1, 15 4))'::geometry) as the_geom;
by copying it into the terminal in the link and press "map1"
Then, since it is not possible to make a geometry of the exterior … ) as a,
'LINESTRING(0 5, 10 6, 12 3, 20 3)'::geometry as b) t
Is this what you were thinking about? …
- 13.3k
7
votes
Accepted
Simulating the expansion of polygon features
it at http://postgisonline.org/map.php
Just copy the sql-code below and click "map1"
WITH RECURSIVE t(the_geom, n) AS (
SELECT 'POLYGON((10 10,8 13, 10 15, 12 14, 15 15, 16 12, 15 10, 10 10))'::geometry … Regards
Nicklas
This one was even nicer I think:
WITH RECURSIVE t(the_geom, n) AS (
SELECT 'POLYGON((10 10,8 13, 10 15, 12 14, 15 15, 16 12, 15 10, 10 10))'::geometry AS the_geom, 1 as n
UNION ALL …
- 13.3k
3
votes
Real-world example of Affine Transform?
From PostGIS doc:
"ST_Affine — Applies a 3d affine transformation to the geometry to do things like translate, rotate, scale in one step."
Here comes a quite dirty example. … The query sent to PostGIS, makes a simplified buffer around the geometry in the right pixelscale and recalculates since the image map has it's origin in upper left corner and the projection of the map …
- 13.3k
0
votes
Is there a PostGIS function to get a tangent and normal line?
I guess you are talking about curves?
What parameters do you want as input?
If you use ST_Shortestline with a point at some distance from your curve/linestring, you will get a line perpenicular from …
- 13.3k
6
votes
Accepted
When would a PostGIS geometry compare using ~= return true when ST_Equals returns false?
As the doc says ~= only compares bounding boxes.
So if you move a point in a way that it doesn't change the bounding box ~= still returns true.
- 13.3k
1
vote
Accepted
What information is stored in a PostGIS geometry and how can I access it?
Here you can see how data is stored
https://trac.osgeo.org/postgis/browser/trunk/liblwgeom/g_serialized.txt
To access for instace srid use st_srid
With other geometry access functions you can get information …
- 13.3k
2
votes
Accepted
PostGIS algorithm to unite points of two geometries that are within specified radius
ST_ConcaveHull should solve this.
- 13.3k
5
votes
Accepted
Use Postgis to convert wkb_geometry data type to geom datatype
You already have the geom type. wkb_geometry is just the name of the column. I see it is a confusing naming since thebstorage isn't wkb but a internal PostGIS format that is quite similar to wkb. I gu …
- 13.3k
0
votes
How to get MultiPolygon from MultiPoint for area calculation in Postgis?
Update
To add the first point at the end of the linestring to get a closed ring you can do something like:
WITH a AS
(SELECT 'multipoint(1 1, 2 1, 2 2, 2 1)'::geometry p)
,b AS
(SELECT ST_LineFromMultiPoint …
- 13.3k
3
votes
Calculate centroid of a point cluster
I am not sure I really understand what you are doing.
How can a point cluster be a collection of linestrings?
, but ..
Remember you are using a spatial database, why not use the functionality in PostG …
- 13.3k
23
votes
What are Definition, Algorithms and Practical Solutions for Concave Hull?
There is an implementation of ST_ConcaveHull in PostGIS trunk.
http://postgis.net/docs/ST_ConcaveHull.html
- 13.3k