Changes between Version 14 and Version 15 of UsersWikiplpgsqlfunctions

Timestamp:

Sep 10, 2009, 4:36:38 PM (15 years ago)

Author:

bcrosby

Comment:

—

UsersWikiplpgsqlfunctions

@@ -22 +22 @@
     endpointutm geometry;
   BEGIN
-        arcenterutm := st_transform(arcenter,utmzone(arcenter));
-        startpointutm := st_transform(startpoint,utmzone(startpoint));
-        endpointutm := st_transform(endpoint,utmzone(endpoint));
+        arcenterutm := st_transform(arcenter,utmzone(arcenter));
+        startpointutm := st_transform(startpoint,utmzone(startpoint));
+        endpointutm := st_transform(endpoint,utmzone(endpoint));
 
-        midpointrads := abs(st_azimuth(arcenterutm,startpointutm) - st_azimuth(arcenterutm,endpointutm))/2;
+        midpointrads := abs(st_azimuth(arcenterutm,startpointutm) - st_azimuth(arcenterutm,endpointutm));
+        IF midpointrads > pi() THEN midpointrads:= (midpointrads - pi())/2; ELSE midpointrads:= midpointrads/2; END IF;
+
         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)||')';
+        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;
@@ -35 +37 @@
   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 (clockwise: \'cw\', conter-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.'; 
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