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Results tagged with algorithm
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user 960
A mathematical procedure used to solve problems with a series of steps. Algorithms are usually encoded as a sequence of computer commands.
11
votes
Accepted
Clustering undirected lines
If I understand you right you want to cluster lines that is about the same without respect to direction.
Here is an idea that I think could work.
split the lines in start point and end point
Cluste …
- 13.3k
3
votes
Lines to Polygons
Hallo
I don't think what you are looking for is a specific algorithm. The task can be quite difficult or very simple depending on your dataset. …
- 13.3k
1
vote
How to incrementally add points to a polygon and eventually increasing the size of the polyg...
I am not sure I understand what you want and I don't see the use case.
It seems like you want to define the polygons and let them increase in size.
Then you have to decide what identifies a polygon …
- 13.3k
11
votes
Map matching links and ideas?
The projecting of points onto the line as you are already doing is possible to do directly in PostGIS.
I wrote about is some time ago, here
But to solve your problem when the points is closer to wro …
4
votes
Algorithms for matching segments
If you tear apart one of the linestrings to compare and test if the vertexpoints is within some distance from the other linestring to compare you can control the test in many ways.
those examples work …
- 13.3k
3
votes
Finding boundary co-ordinates from given set of point co-ordinates?
What you want is the Convex hull. In PostGIS there is a function (actually GEOS) that gives you the Convex hull, ST_ConvexHull(geometry).
At wikipedia there is a lot of info about concave hulls.
- 13.3k
1
vote
Point in polygon algorithm for multiple polygons
In postgis ST_Intersects uses indexes to first find if the point is inside the bounding box of the polygon and then makes a recheck to see if it really is inside the polygon. That is fast, often very …
- 13.3k
2
votes
Algorithm to find polygons enclosing points
from a database perspective it sounds like you want to group the points on the ilands and make a convexhull on each group.
in postgis it would look something like:
SELECT ST_Convexhull(ST_Collect(p. …
- 13.3k
2
votes
How to bring polygons closer to a point?
making the polygons bigger should give the desired effect.
http://postgis.net/docs/manual-1.5/ST_Scale.html
/Nicklas
- 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
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