[postgis-users] Get concave hull from an array of longitude in latitude points

[Aleš Kecman]

Hi!

I'm still struggling with this "concave hulls" and it seems I just can't
find the way how to do it. I'm sending a text file with some longitude and
latitude points of selected subarea from which I need to get a concave
polygon. There is only one polygon in attached text file. In my database I
have around 500 000 points from which I need to form around 700 polygons. If
there is a way to do it in PostGis I would really appreciate any help. I
also attached a jpg picture of my convexhull polygon. Thanks!!!

Greets, Ales.



On Mon, Nov 24, 2008 at 12:13 PM, Mark Cave-Ayland <
mark.cave-ayland at siriusit.co.uk> wrote:

> Aleš Kecman wrote:
>
>> Hi!
>>
>>
>> I'm new to Postgis and would really like to get some help on getting a
>> concave hull from an array of points.
>>
>> For example:
>>
>> I have an array of points - longitude and latitude of buildings in
>> particular area in the city. I already managed to get a convex hull polygon
>> from this array of points, but this is not really helpful. What I'm trying
>> to get is some kind of concave hull polygon from an array of points, which I
>> would further like to use in Google Earth kml file.
>>
>> Thanks.
>>
>
>
> Hi Aleš,
>
> Does ST_Union() help you at all?
>
>
> ATB,
>
> Mark.
>
> --
> Mark Cave-Ayland
> Sirius Corporation - The Open Source Experts
> http://www.siriusit.co.uk
> T: +44 870 608 0063
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