[postgis-users] Section of Circle from 3 Points and Convert to Linestring

Randall, Eric ERandall at eriecountygov.org
Wed Jun 11 17:47:27 PDT 2008

What a great bunch of GeoSkirmishers you are!
Here is another question.

I have a line AB where A is (0,0) and B is (10,0).
I also have a point P that is (5,3).
I know that the section of the circle that passes through A,P, and B
can be determined if I know the circle center - point C, which
can be defined as the intersection of perpendicular lines projected
from the midpoints of AP and BP.  

What is the most economical way of expressing this using PostGIS/PostgreSQL fuctions?
Alternatively, if there is a better approach, what is that? Thanks!


Eric Randall
County of Erie, Pa.

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