Contents
How to solve the non noded intersection problem in PostGIS?
In postgis ST_Node should break a series of lines at intersections, which should solve the non-noded intersection problem. Wrapping this in ST_Dump generates the composite array of the broken lines.
When to skip the St _ intersection call in PostGIS?
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: This kind of question comes up a lot: As discussed in stackexchange Acquiring ArcGIS speed in PostGIS
Is the PostGIS extension no longer allow relocation?
As of PostGIS 2.3, the postgis extension was changed to no longer allow relocation. All function calls within the extension are now schema qualified.
Why do I get error PostGIS backend is already set?
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. After upgrading to Postgis 2.3 from 2.1, my server log is filled with these messages : Read more…
When to use sfgcal based St _ intersection-PostGIS?
If working with 3D geometries, you may want to use SFGCAL based ST_3DIntersectionwhich does a proper 3D intersection for 3D geometries. Although this function works with Z-coordinate, it does an averaging of Z-Coordinate values when postgis.backend=geos. postgis.backend=sfcgal, it will return a 2D geometry regardless ignoring the Z-Coordinate.
When to use St _ intersection and St _ intersects?
ST_Intersection in conjunction with ST_Intersects is very useful for clipping geometries such as in bounding box, buffer, region queries where you only want to return that portion of a geometry that sits in a country or region of interest. Geography: For geography this is really a thin wrapper around the geometry implementation.
Can a PostGIS be compiled with sfcgal support?
If your PostGIS is compiled with sfcgal support, have option of using sfcgal, but note if basically cases down both geometries to 2D before doing intersection and returns the ST_Force2D equivalent result which is a 2D geometry