Changes between Version 20 and Version 21 of UsersWikiplpgsqlfunctions

Timestamp:

Nov 24, 2009, 8:54:12 AM (14 years ago)

Author:

bcrosby

Comment:

—

UsersWikiplpgsqlfunctions

@@ -6 +6 @@
 [wiki:UsersWikiplpgsqlfunctionsDistance Distance /Spatial Reference support functions PL/PGSQL/SQL Functions]
 
- * '''Generate an arc given two points on the arc, the centre point and direction'''
+ * '''Generate an arc given two points on the arc, the centre point and direction or size'''
 
 {{{
 #!sql
- CREATE OR REPLACE FUNCTION st_createarc(startpoint geometry, endpoint geometry, arcenter geometry,direction text)
-  RETURNS geometry AS
-  $$
+ CREATE FUNCTION st_createarc(startpoint geometry, endpoint geometry, arcenter geometry, direction text) RETURNS geometry
+    AS $$
   DECLARE
-    pointonarc geometry;
-    thearc text;
-    thedirection float;
+    cwpointonarc geometry;
+    ccpointonarc geometry;
+    ccarc text;
+    cwarc text;
+    cwdirection float;
+    ccdirection float;
     midpointrads float;
     arcenterutm geometry;
     startpointutm geometry;
     endpointutm geometry;
+    thearc geometry;
+    majorarc text;
+    minorarc text;
   BEGIN
         arcenterutm := st_transform(arcenter,utmzone(arcenter));
@@ -30 +35 @@
         IF midpointrads > st_azimuth(arcenterutm,startpointutm) THEN midpointrads:= st_azimuth(arcenterutm,startpointutm)/2; END IF;
         IF midpointrads > st_azimuth(arcenterutm,endpointutm) THEN midpointrads:= st_azimuth(arcenterutm,endpointutm)/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)||')';
-        RETURN st_transform(st_setsrid(st_curvetoline(thearc),utmzone(arcenter)),st_srid(arcenter));
+        cwdirection := -1*midpointrads;
+ccdirection := midpointrads;
+cwpointonarc := ST_Translate( ST_Rotate( ST_Translate( startpointutm, -1*ST_X(arcenterutm), -1*ST_Y(arcenterutm)), cwdirection), ST_X(arcenterutm), ST_Y(arcenterutm));
+ccpointonarc := ST_Translate( ST_Rotate( ST_Translate( startpointutm, -1*ST_X(arcenterutm), -1*ST_Y(arcenterutm)), ccdirection), ST_X(arcenterutm), ST_Y(arcenterutm));
+        cwarc := 'CIRCULARSTRING('||ST_X(startpointutm)||' '||ST_Y(startpointutm)||','||ST_X(cwpointonarc)||' '||ST_Y(cwpointonarc)||','||ST_X(endpointutm)||' '||ST_Y(endpointutm)||')';
+ccarc := 'CIRCULARSTRING('||ST_X(startpointutm)||' '||ST_Y(startpointutm)||','||ST_X(ccpointonarc)||' '||ST_Y(ccpointonarc)||','||ST_X(endpointutm)||' '||ST_Y(endpointutm)||')';
+IF st_length(st_curvetoline(cwarc)) > st_length(st_curvetoline(ccarc)) THEN majorarc := cwarc; minorarc := ccarc; ELSE majorarc := ccarc; minorarc := cwarc; END IF;
+IF direction = 'major' THEN RETURN st_transform(st_setsrid(st_curvetoline(majorarc),utmzone(arcenter)),st_srid(arcenter)); ELSE IF direction = 'minor' THEN RETURN st_transform(st_setsrid(st_curvetoline(minorarc),utmzone(arcenter)),st_srid(arcenter)); END IF; END IF;
+        IF direction = 'cw' THEN RETURN st_transform(st_setsrid(st_curvetoline(cwarc),utmzone(arcenter)),st_srid(arcenter)); ELSE IF direction = 'cc' THEN RETURN st_transform(st_setsrid(st_curvetoline(ccarc),utmzone(arcenter)),st_srid(arcenter)); END IF; END IF;
   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 (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.'; 
+  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\', or size \'major\' or \'minor\'). 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.';