Changes between Version 12 and Version 13 of UsersWikiplpgsqlfunctions

Timestamp:

Sep 10, 2009, 11:16:44 AM (15 years ago)

Author:

bcrosby

Comment:

—

UsersWikiplpgsqlfunctions

@@ -16 +16 @@
     thearc text;
     thedirection float;
+    midpointrads float;
+    originalsrid int;
+    arcenterutm geometry;
+    startpointutm geometry;
+    endpointutm geometry;
   BEGIN
-        IF direction = 'cc' THEN thedirection := pi()/5; ELSE thedirection := -1*pi()/5; END IF;
-        pointonarc := ST_Translate( ST_Rotate( ST_Translate( startpoint, -1*ST_X(arcenter), -1*ST_Y(arcenter)), thedirection), ST_X(arcenter), ST_Y(arcenter));
-        thearc := 'CIRCULARSTRING('||ST_X(startpoint)||' '||ST_Y(startpoint)||','||ST_X(pointonarc)||' '||ST_Y(pointonarc)||','||ST_X(endpoint)||' '||ST_Y(endpoint)||')';
-        RETURN st_transform(st_curvetoline(st_transform(st_setsrid(thearc,st_srid(arcenter)),utmzone(arcenter))),st_srid(arcenter));
+        arcenterutm := st_transform(arcenter,utmzone(arcenter));
+        startpointutm := st_transform(startpoint,utmzone(startpoint));
+        endpointutm := st_transform(endpoint,utmzone(endpoint));
+
+        midpointrads := abs(st_azimuth(startpointutm,arcenterutm) - st_azimuth(endpointutm,arcenterutm))/2;
+        IF direction = 'cw' THEN thedirection := -1*midpointrads; ELSE thedirection := midpointrads; END IF;
+        pointonarc := ST_Translate( ST_Rotate( ST_Translate( startpointutm, -1*ST_X(arcenterutm), -1*ST_Y(arcenterutm)), thedirection), ST_X(arcenterutm), ST_Y(arcenterutm));
+        thearc := 'CIRCULARSTRING('||ST_X(startpointutm)||' '||ST_Y(startpointutm)||','||ST_X(pointonarc)||' '||ST_Y(pointonarc)||','||ST_X(endpointutm)||' '||ST_Y(endpointutm)||')';
+        RETURN st_transform(st_setsrid(st_curvetoline(thearc),utmzone(arcenter)),st_srid(arcenter));
   END;
   $$
   LANGUAGE 'plpgsql' IMMUTABLE;
-  COMMENT ON FUNCTION st_createarc(geometry,geometry,geometry,text) IS 'Generates an arc based on starting point, ending point,centre of arc, and direction. All geometries must be of type POINT and direction must be "cc" (counter-clockwise) or "cw" (clockwise).This function returns a linestring of the arc based on the original SRID and 32 points per quarter circle. Requires the utmzone function.'; 
- 
+  COMMENT ON FUNCTION st_createarc(geometry,geometry,geometry,text) IS 'Generates an arc based on starting point, ending point, centre of arc, and direction (clockwise: 'cw', counter-clockwise: 'cc'). All geometries must be of type POINT and this function returns a linestring of the arc based on the original SRID and 32 points per quarter circle. Requires the utmzone function.'; 
+
 }}}