Doing an ST_Intersection is much slower than relation checks such as ST_Intersects , 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:

1. geometry a is …

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Every one or two months, someone asks on the PostGIS users list usually somewhat panicked, My geometry is missing when I look in pgAdmin III

This is documented in the PostGIS Frequently Asked questions section of the manual I tried to use PgAdmin to view my geometry column and it is blank, what gives?

Since this …

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People often get confused between the ST_Transform and ST_SetSRID functions.

1. 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 …

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If you have a problem that involves finding the things within X distance of other things or finding what things have nothing within X distance do not use ST_Distance for filtering and also do not try to use ST_Intersects + ST_Buffer. Use ST_DWithin instead. Why?

1. ST_DWithin can use an index and ST_Distance can not …

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In mapping frameworks spatial coordinates are often in order of latitude and longitude. In spatial databases spatial coordinates are in x = longitude, and y = latitude.

If you accidentally loaded data as lat,lon, you can always fix the mistake by using the ST_FlipCoordinates function introduced in PostGIS 2.0.

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