[postgis-users] raster regions

[Pierre Racine]

Hi,

That could translate into something like this in PostGIS:

WITH floodareas AS (
  SELECT ST_MapAlgebra(rast, ‘1BB’, ‘CASE WHEN [rast] < 10 THEN 1 ELSE NULL END’) rast
  FROM elevation
)
SELECT d.*
FROM districts d, floodareas f
WHERE ST_Intersects(g.geom, f.rast)

NULL becomes nodata values. You could also use ST_Reclass() instead of ST_Mapalgebra().

Pierre

De : postgis-users <postgis-users-bounces at lists.osgeo.org> De la part de Joao Cordeiro
Envoyé : 15 juillet 2019 10:19
À : 'PostGIS Users Discussion' <postgis-users at lists.osgeo.org>
Objet : [postgis-users] raster regions


Hi there,

I am not actually a POSTGIS user, or developer, although I am doing some research of integration of vector -raster in a dbms context. My main question s about identifying regions represented in a domain like the "hybrid raster" so that they can be referred to in a query. For example, I would like to write something like "select d from districts where d.geometry touches flooding", where "flooding" indicates an expression intended to decide on the pertinence of locations to a flooding ​​risk area described, for instance through map algebra.

Thanks for any hints or suggestions.

Att.
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