Thanks Nicolas,
I've gotten a bit farther. Stuck again though. This works:
SELECT
ST_AsText(ST_ConvexHull(ST_Collect(ST_GeomFromText('MULTIPOINT(50.569455
-111.868842, 50.569992 -111.898634, 50.583764 -111.907919, 50.569452
-111.868859)') ) ));
st_astext
--------------------------------------------------------------------------------------------------------------------------
POLYGON((50.583764 -111.907919,50.569992 -111.898634,50.569452
-111.868859,50.569455 -111.868842,50.583764 -111.907919))
But for some reason, I can't update:
UPDATE territories SET border =
ST_ConvexHull(ST_Collect(ST_GeomFromText('MULTIPOINT(50.569455 -111.868842,
50.569992 -111.898634, 50.583764 -111.907919, 50.569452 -111.868859)') ) )
WHERE id = 3014;
ERROR: cannot use aggregate function in UPDATE
LINE 1: UPDATE territories SET border = ST_ConvexHull(ST_Collect(ST_...
Any ideas? I'm new to these functions.. Ultimately, I want to update territory
with a set of points from a SELECT, e.g.:
SELECT location FROM addresses WHERE territory_id = 3014;
Table "public.addresses"
Column | Type | Modifiers
| Storage | Description
-----------------+--------------------------+--------------------------------------------------------+----------+-------------
id | integer | not null default
nextval('addresses_id_seq'::regclass) | plain |
territory_id | integer | not null
| plain |
location | geography(Point,4326) |
| main |
On 2012-09-10, at 12:46 PM, Nicolas Ribot wrote:
> Hi,
>
> You could use st_convexHull on the point set and then buffer it with
> st_buffer.
> (st_concaveHull may give you better results on polygon approximation
> (see:
> http://postgis.refractions.net/documentation/manual-2.0/ST_ConcaveHull.html)
>
> Nicolas
>
> On 10 September 2012 20:39, René Fournier <m...@renefournier.com> wrote:
>> I've written a script to migrate location data from MySQL to PostGIS.
>> Each region contains 5-20 locations. I would like my script to create a
>> simple polygon for each region that encompasses its locations (lat/lng
>> points). I say simple in the sense of not too many vertices (< 10), even if
>> the region contains 20 points.(The easiest thing would be a bounding box,
>> but I would like it a bit more defined than that.) Additionally, I would
>> like the polygon to be a bit bigger (say, by 10 meters) than the points it
>> contains.
>>
>> Just wondering if this is something that can be done in a PostGIS query or
>> PHP using some algorithm for simple. What would you recommend? Thanks!
>>
>> ...Rene
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