[postgis-users] Construcción de multipunto a partir de puntos en polígono

[Felix Kunde]

Hi Nestor,

de nada.
You forgot the GROUP BY clause in your query. If you add GROUP BY patrulla.id at the end of your query you should get a MultiPoint geometry per polygon.

Have a nice weekend.
Felix 
 

Gesendet: Freitag, 20. April 2018 um 16:45 Uhr
Von: "Néstor Ramires" <nramire1 at rosario.gov.ar>
An: postgis-users at lists.osgeo.org, "Felix Kunde" <felix-kunde at gmx.de>
Betreff: Re: [postgis-users] Construcción de multipunto a partir de puntos en polígono
¡Gracias Felix!
Si, sería el ST_Collect la función que estaba buscando.

Realicé unas pruebas y hasta ahora sólo conseguí que construya un multipunto de todos los objetos de la tabla arboles.

CREATE TABLE pepe2 AS (
SELECT ST_Multi(ST_Collect(r.raiz)) AS puntito
FROM (
SELECT (ST_Dump(raiz)).geom AS raiz
FROM arboles, patrulla p
WHERE ST_Contains(p.region, arboles.raiz)
) AS r);

El objetivo es que construya un multipunto por cada póligono, utilizando todos los puntos que contiene ése polígono. No me doy cuenta de dónde hacer la discriminación por puntos contenidos en polígonos.
Me pueden orientar en la resolución de este ejercicio.

-----------------------------------

Thanks Felix!
Yes, it would be the ST_Collect function that I was looking for.

I made some tests and until now I only managed to build a multipoint of all the objects in the trees table.

CREATE TABLE pepe2 AS (
SELECT ST_Multi(ST_Collect(r.raiz)) AS puntito
FROM (
SELECT (ST_Dump(raiz)).geom AS raiz
FROM arboles, patrulla p
WHERE ST_Contains(p.region, arboles.raiz)
) AS r);

The objective is to build a multipoint for each poligono, using all the points that this polygon contains. I do not realize where to do the discrimination for points contained in polygons.
You can guide me in the resolution of this exercise.


En Wed, 18 Apr 2018 13:00:34 -0300, Felix Kunde <felix-kunde at gmx.de> escribió:

> Hola Nestor,
> I guess, what you're looking for is ST_Collect. ST_Multi is not an aggregate function. It's only useful if you need to bring all rows of a column into a multi representation.
> Salduos
> Felix
>
> Gesendet: Mittwoch, 18. April 2018 um 16:18 Uhr
> Von: "Néstor Ramires" <nramire1 at rosario.gov.ar>
> An: "PostGIS Users Discussion" <postgis-users at lists.osgeo.org>
> Betreff: [postgis-users] Construcción de multipunto a partir de puntos en polígono
>
> Hola a todos
> Tengo los siguientes datos:
>
> CREATE TABLE arboles (
> id SERIAL,
> raiz geometry(Point, 22185)
> );
>
> INSERT INTO arboles (raiz) VALUES (ST_GeomFromText('POINT(1 1)',22185));
> INSERT INTO arboles (raiz) VALUES (ST_GeomFromText('POINT(1 2)',22185));
> INSERT INTO arboles (raiz) VALUES (ST_GeomFromText('POINT(5 2)',22185));
> INSERT INTO arboles (raiz) VALUES (ST_GeomFromText('POINT(6 2)',22185));
> INSERT INTO arboles (raiz) VALUES (ST_GeomFromText('POINT(5 3)',22185));
> INSERT INTO arboles (raiz) VALUES (ST_GeomFromText('POINT(1 6)',22185));
> INSERT INTO arboles (raiz) VALUES (ST_GeomFromText('POINT(3 6)',22185));
>
>
> CREATE TABLE patrulla (
> id SERIAL,
> guardia int,
> arboles geometry(MultiPoint, 22185),
> region geometry(Polygon, 22185)
> );
>
> INSERT INTO patrulla (guardia, region) VALUES (1, ST_GeomFromText('POLYGON((0 0, 0 3, 3 3, 3 0, 0 0))',22185));
> INSERT INTO patrulla (guardia, region) VALUES (2, ST_GeomFromText('POLYGON((4 1, 4 4, 8 4, 8 1, 4 1))',22185));
> INSERT INTO patrulla (guardia, region) VALUES (3, ST_GeomFromText('POLYGON((2 8, 0 6, 2 4, 2 8))',22185));
> INSERT INTO patrulla (guardia, region) VALUES (4, ST_GeomFromText('POLYGON((2 8, 5 6, 2 4, 2 8))',22185));
>
> El objetivo es actualizar el campo arboles de la tabla patrulla, con una geometría multipunto que contenga todos los árboles de la región. Para ello utilizo la siguiente sentencia:
>
> UPDATE patrulla mpSET arboles = ST_Multi(r.raiz)
> FROM arboles r
> WHERE ST_Contains(mp.region, r.raiz);
>
> Que no estaría funcionando como yo esperaba, ya que en las regiones que tienen más de un árbol en su interior, sólo toma en cuenta el primero de ellos.
> ¿Alguno puede darme una idea de por dónde apuntar para buscar la solución?
>
> --------------------------------------------------
> Hello everyone
> I have the following data:
>
> CREATE TABLE arboles (
> id SERIAL,
> raiz geometry(Point, 22185)
> );
>
> INSERT INTO arboles (raiz) VALUES (ST_GeomFromText('POINT(1 1)',22185));
> INSERT INTO arboles (raiz) VALUES (ST_GeomFromText('POINT(1 2)',22185));
> INSERT INTO arboles (raiz) VALUES (ST_GeomFromText('POINT(5 2)',22185));
> INSERT INTO arboles (raiz) VALUES (ST_GeomFromText('POINT(6 2)',22185));
> INSERT INTO arboles (raiz) VALUES (ST_GeomFromText('POINT(5 3)',22185));
> INSERT INTO arboles (raiz) VALUES (ST_GeomFromText('POINT(1 6)',22185));
> INSERT INTO arboles (raiz) VALUES (ST_GeomFromText('POINT(3 6)',22185));
>
>
> CREATE TABLE patrulla (
> id SERIAL,
> guardia int,
> arboles geometry(MultiPoint, 22185),
> region geometry(Polygon, 22185)
> );
>
> INSERT INTO patrulla (guardia, region) VALUES (1, ST_GeomFromText('POLYGON((0 0, 0 3, 3 3, 3 0, 0 0))',22185));
> INSERT INTO patrulla (guardia, region) VALUES (2, ST_GeomFromText('POLYGON((4 1, 4 4, 8 4, 8 1, 4 1))',22185));
> INSERT INTO patrulla (guardia, region) VALUES (3, ST_GeomFromText('POLYGON((2 8, 0 6, 2 4, 2 8))',22185));
> INSERT INTO patrulla (guardia, region) VALUES (4, ST_GeomFromText('POLYGON((2 8, 5 6, 2 4, 2 8))',22185));
> The objective is to update the Trees field of the patrol table, with a multipoint geometry that contains all the trees in the region. To do this I use the following sentence:
>
> UPDATE patrulla mpSET arboles = ST_Multi(r.raiz)
> FROM arboles r
> WHERE ST_Contains(mp.region, r.raiz);
> That would not be working as I expected, as in regions that have more than one tree inside, just take into account the first of them.
> Can anyone give me an idea of where to aim to find the solution?_______________________________________________ postgis-users mailing list postgis-users at lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/postgis-users
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