CODEWITHSUNDEEP
mergeclassificationpostgis
j_rah14
j_rah14

Reputation: 23

POSTGIS: Dissolve Multi-polygons to enable joined classification

I have a number of spatial database, through which I have identified particular types of land-cover. The topographic layer [defining land-cover] is made up of multi-polygons and I am using a separate point layer in order to join a classification type to it. However, the areas portrayed in the topographic layer may be formed from several individual polygons, without a total perimeter outline to identify the area. Therefore, the classification point may sit in just one individual polygon of the overall area [see below].

Example. Image is of a park, which consists of over 20 individual polygons. The point that classifies the area as a park sits within one of the polygons and cannot be attached to the entire area. Example

I would like to be able to apply the point based classification to the whole park area. I have tried to use ST_UNION function in order to do such, but have been unable. Does anyone know of a way to dissolve the area into a single shape/remove the pathways? This is a small example of a much larger data set, where there is little scope of manually defining area sand buffers in order to classify the data, thus I wondered if there was a practicable solution.

If anyone can help, it would be hugely appreciated....

Upvotes: 1

Views: 2137

Answers (1)

Anoop J
Anoop J

Reputation: 267

SELECT ST_Collect(t.the_geom) as singlegeom FROM TABLE t; http://postgis.net/docs/ST_Collect.html

Upvotes: 0

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