Changes between Version 10 and Version 11 of UsersWikiplpgsqlfunctions


Ignore:
Timestamp:
Sep 9, 2009, 9:42:53 AM (15 years ago)
Author:
bcrosby
Comment:

added function to generate an arc.

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  • UsersWikiplpgsqlfunctions

    v10 v11  
    44
    55==  This is an area to put utility functions or wrappers around PostGIS ==
     6
     7 * '''Generate an arc given two points on the arc and the centre point'''
     8
     9{{{
     10#!sql
     11 CREATE OR REPLACE FUNCTION st_createarc(startpoint geometry, endpoint geometry, arcenter geometry)
     12  RETURNS geometry AS
     13  $$
     14  DECLARE
     15    pointonarc geometry;
     16    thearc text;
     17  BEGIN
     18        pointonarc := ST_Translate( ST_Rotate( ST_Translate( startpoint, -1*ST_X(arcenter), -1*ST_Y(arcenter)), pi()/5), ST_X(arcenter), ST_Y(arcenter));
     19    thearc := 'CIRCULARSTRING('||ST_X(startpoint)||' '||ST_Y(startpoint)||','||ST_X(pointonarc)||' '||ST_Y(pointonarc)||','||ST_X(endpoint)||' '||ST_Y(endpoint)||')';
     20        RETURN st_transform(st_curvetoline(st_transform(st_setsrid(thearc,st_srid(arcenter)),utmzone(arcenter))),st_srid(arcenter));
     21  END;
     22  $$
     23  LANGUAGE 'plpgsql' IMMUTABLE;
     24  COMMENT ON FUNCTION st_createarc(geometry,geometry,geometry) IS 'Generates an arc based on starting point, ending point and centre of arc. 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.';
     25}}}
    626
    727 * '''Find UTM (WGS84)  SRID for a point (in any SRID)'''