[postgis-users] Difficult Problem with Polygons

[Ed Linde]

Hi All,
I need help with 2 hard problems. I store triangles in a table as POLYGON.

1. I want to know for a given triangle, which triangles share an edge
(adjacent) with this triangle.

2. Then I have a line that cuts through a triangle's face and a point Q,
away from this line and
triangle. I would like to know amongst the neighbours of the triangle
(calculated in 1),
which ones fall *below* the line and closer to the point Q (where Q is the
generator of a Voronoi cell).
And also the set of triangles that are *above* the line and further from Q.

Any suggestions as to how I can go about achieving this in postgis 2.0?

Cheers,
Ed
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