I have a table with points and another table with polygons (multipolyons to be more accurate). How do I find the points that fall within a specified distance of the polygon's border? Most of the points fall within a polygon but I want a list of points that fall within 100 meters of a polygon edge. If a point is 20 meters from a boundary that is shared by adjacent polygons, I'd expect that point to be listed within 100 meters of two polygons.
The SQL below selects too many points. It select points inside the polygon but outside the interior buffer. It should not select points inside the polygon and greater than 100 meters from the edge.
select * from towers t, areas c where st_dwithin(t.geom, c.geom, 100.00) order by t.description
How do I modify this query to return points that are within 100 meters of a polygon's boundary, not necessarily all points within the poylgon?