select a.saps_label from localauthorities a, localauthorities b
where st_touches(a.the_geom, b.the_geom)
and b.saps_label like '%Kerry%';
select astext(the_geom), classdesc from archeology
where classdesc like '%Castle%';
Polygon-on-polygon
Overlay of two or more layers results in more complex output layer
Polygon = group of cells
c = (z1 + 2z2 + z3 - z7 - 2z8 - z9) / 8D
D is the spacing of points (30 m)
weighting four closer neighbours higher