Functions for the geography type
Great Circle Mapper
Great Circle Mapper is a website that shows lines on the globe that follow great circles, which is analogous to the shortest travel direction a plane would take between locations. The logic used for great circles is the same used for PostGIS' geography type.
This helper function returns a URL for the Great Circle Mapper website that shows the path of a geography linestring on the Earth.
CREATE FUNCTION ST_AsGreatCircleMapperURL(geography) RETURNS text AS $BODY$SELECT 'http://www.gcmap.com/mapui?P=' || string_agg( abs(ST_Y(geom))::text || CASE WHEN ST_Y(geom) < 0 THEN 'S' ELSE 'N' END || '+' || abs(ST_X(geom))::text || CASE WHEN ST_X(geom) < 0 THEN 'W' ELSE 'E' END, '-') || '&MS=wls&DU=km' AS url FROM ST_DumpPoints($1::geometry)$BODY$ LANGUAGE sql IMMUTABLE;
SELECT ST_AsGreatCircleMapperURL('POLYGON ((35 10, 45 45, -15 40, -10 20, 35 10))'::geography);
SELECT ST_AsGreatCircleMapperURL(ST_MakeEnvelope(-75, -80, 110, 3)::geography);