The error 'postgis.backend' is already set comes up every so often in PostGIS mailing list.
The issue arises often during or after an upgrade. I'll go over causes for this I am aware of and how to fix.
The question goes something like this
After upgrading to Postgis 2.3 from 2.1, my server log is
filled with these … Read More
This raster question comes up quite a bit on PostGIS mailing lists and stack overflow and the best answer often involves
the often forgotten ST_Reclass function that has existed since PostGIS 2.0.
People often resort to the much slower though more flexible ST_MapAlgebra or dumping out
their rasters as Pixel valued …
PostGIS 2.2.0 came out this month, and the SFCGAL extension that offers advanced 3D and volumetric support, in addition to some extended 2D functions like ST_ApproximateMedialAxis became a standard PostgreSQL extension
and seems to be a fairly popular extension.
I've seen several reports on GIS Stack Exchange of people …
PostGIS raster has so so many functions and probably at least 10 ways of doing something some much much slower than others. Suppose
you have a raster, or you have a raster area of interest -- say elevation raster for example, and you want to know the distinct pixel values in the area.
The temptation is to reach for …
Doing an ST_Intersection is much slower than relation checks such as
, ST_CoveredBy, and , ST_Within .
In many situations you know the intersection of 2 geometries
without actually computing an intersection. In these cases, you can skip the costly ST_Intersection call. Cases like this:
ST_SetSRID doesn't change the coordinates but adds meta data to state what spatial reference system the coordinate actually are.
If you stamped your WGS 84 long lat data as a meter based projection. Guess what? Its still long lat.
A spade …