[postgis-users] Intersection between circles

[Yves Moisan]

Thanx for your reply Maxime.

Yves

> On 08/12/09 16:33, Yves Moisan wrote:
> > So from adbea to (acba + adebca)
> > 
> > I know the distances from both a and b and I need to draw segments bc
> > and ac, so I need to find the intesection of the two circles centered at
> > a and b with the known radii I have.  Is there a function that would
> > return the two intersection points of the circles and preferably only
> > the one contained in my polygon ?
> 
> I don't think there is such a function but I see at least two other
> solutions:
> 
> 1 - Approximate the circle by constructing a linestring with many of
> segments (I use 50 to 200 segments for the whole cirlce depending on the
> precesion I need). Using ST_Intersect and ST_Within will let you
> determine C quite easily.
> 
> 2 - Use some trigonometry to determine c by other means (like working
> with the two right-angled triangles contained in acb).
>