User:Maxbe/Satteldrehung nach Höhenlinien/getsaddledirection

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Quelltext zur Satteldrehung nach Höhenlinien ohne langatmige Beschreibung:

-- FUNCTION INTEGER getsaddledirection(Point:GEOMETRY in Mercator, Direction: Text)
-- --------------------------------------------------------------------------------
-- returns the direction of a saddle at (Point) in degrees (0deg...179deg) (0:north 90:east 180:south)
-- Constants
--    SearchArea:   limit where the next contour line must be (in meters)
--    SearchLimit:  maximum number of examined contour lines
--    MinDescent:   minimum distance to go down the slope and search for the next lower contour line (in units of your contour lines, normally meters)
--    ErrorReturn:  direction which is returned in case of errors
-- Algorithm:
--    get the mappers oppinion about the direction, try to parse the value as number
--    if that doesn't work:
--     get a sample of contour lines near the saddle
--     find the next contour line and define its height as "height of this saddle point"
--     find the next contour line which is at least MinDescent lower or higher than the "height of this saddle point", get the closest point on this line
--     get the azimuth between the saddle point and the closest point if the contour line was lower, azimuth+90deg if it was higher
--     for all other contour lines in sample: (get the next contour line, calculate the azimuth and correct the first choice with a weight depending on the distance)
--    if something went wrong, return -135, (this negative return value may be considered as error flag or as "default orientation" nearly to north direction)
-- Requirement:
--    you need a database "contours" with a table "contours" with the columns "height" and "wkb_geometry" (in EPSG:3857)
-- Installation:
--    psql databasename < path_to_me/saddledirection.sql
--    (as owner of the database where the saddles are, eg "gis")
--    You also need to install the extension "dblink", but that you have allready done following "HOWTO_Preprocessing"
--    For "dblink('dbname=mydb', 'select ...')" you have to be superuser or you have to provide a passwort with your query. 
--    Because mapnik is not using the superuser account, the connection to countours is opened with "dblink_connect_u('contours_connection', 'dbname=contours')"
--    and then the query is done with "dblink('contours_connection','select ...')". In this case mapnik just need the execution 
--    right for dblink_connect_u.
--    as postgres
--     psql databasename -c "GRANT EXECUTE ON FUNCTION dblink_connect_u(text) to username;"
--     psql databasename -c "GRANT EXECUTE ON FUNCTION dblink_connect_u(text,text) to username;"
--    as database user (e.g. "gis"
--     psql gis <  saddledirection.sql
--  Test:
--     gis=> select osm_id,name,ele,direction,getsaddledirection(way,direction) from planet_osm_point where osm_id=321173195;   
--     --->  getsaddledirection=94
--     gis=> select osm_id,name,ele,getsaddledirection(way,'east') from planet_osm_point where osm_id=321173195;
--     --->  getsaddledirection=90
--     gis=> update planet_osm_point set direction='93.1' where osm_id=321173195;
--     gis=> select osm_id,name,ele,getsaddledirection(way,direction) from planet_osm_point where osm_id=321173195;
--     --->  getsaddledirection=93
--   Updating all unmapped directions:
--     Getting the direction of a saddle with this funktion needs a lot of time, but it's fast if the direction is allready mapped. Maybe you want to 
--     set the direction of all unmapped saddles from time to time, until OSM has all the directions:
--     psql gis -c "update planet_osm_point set direction=getsaddledirection(way,direction) where \"natural\" in ('saddle','col','notch') and direction is null;"


  SearchArea   CONSTANT INTEGER :=  200;
  SearchLimit  CONSTANT INTEGER :=   10;
  MinDescent   CONSTANT INTEGER :=    5;
  ErrorReturn  CONSTANT INTEGER := -135;

  saddlepoint     TEXT := point::TEXT;
  result          RECORD;
  saddleheight    FLOAT;
  direction       INTEGER;
  thisdirection   INTEGER;
  diffdirection   FLOAT;
  firstdistance   INTEGER;
  SearchAreaMerc  INTEGER;
  querystring     TEXT;
  i               INTEGER;

-- -------------------  First try to parse the given direction ----------------------------------------------------------
  IF     (osmdirection ~ '^[0-9]+$')                                                                                    THEN direction=((osmdirection::INTEGER)+360)%180;
  ELSEIF (osmdirection ~ '^[0-9]+\.[0-9]+$')                                                                            THEN direction=((ROUND(osmdirection::FLOAT)::INTEGER)+360)%180;
  ELSEIF (osmdirection='s'   OR osmdirection='south'           OR osmdirection='n'   OR osmdirection='north')           THEN direction:=0; 
  ELSEIF (osmdirection='ssw' OR osmdirection='south-southwest' OR osmdirection='nne' OR osmdirection='north-northeast') THEN direction:=22;
  ELSEIF (osmdirection='sw'  OR osmdirection='southwest'       OR osmdirection='ne'  OR osmdirection='northeast')       THEN direction:=45;
  ELSEIF (osmdirection='wsw' OR osmdirection='west-southwest'  OR osmdirection='ene' OR osmdirection='east-northeast')  THEN direction:=67;
  ELSEIF (osmdirection='w'   OR osmdirection='west'            OR osmdirection='e'   OR osmdirection='east' )           THEN direction:=90;
  ELSEIF (osmdirection='nw'  OR osmdirection='northwest'       OR osmdirection='se'  OR osmdirection='southeast' )      THEN direction:=135;
  ELSEIF (osmdirection='wnw' OR osmdirection='west-northwest'  OR osmdirection='ese' OR osmdirection='east-southeast')  THEN direction:=112;
  ELSEIF (osmdirection='nnw' OR osmdirection='north-northwest' OR osmdirection='sse' OR osmdirection='south-southeast') THEN direction:=157;
-- -------------------  No given direction: estmate it ----------------------------------------------------------
-- Open connection to database contours, if its not open
   IF ((dblink_get_connections() IS NULL) OR ('saddle_contours_connection' != ANY(dblink_get_connections()))) THEN
    PERFORM dblink_connect_u('saddle_contours_connection', 'dbname=contours');
   END IF;
   select round(SearchArea/cos(st_y(st_transform(st_setsrid(saddlepoint::geometry,3857),4326))/180*3.14159)) INTO SearchAreaMerc;
-- build query string, we need something like
--  "select geom,height,ST_Distance(geom,saddle) FROM contours where st_intersects((saddle,search area),geom) order by distance limit searchlimit;"
   querystring='SELECT wkb_geometry,height,ST_Distance(st_setsrid(wkb_geometry,3857), || saddlepoint || ::geometry) as dist FROM contours WHERE 
                  ST_Intersects(ST_Expand( || saddlepoint || ::geometry,' || SearchAreaMerc || '),st_setsrid(wkb_geometry,3857)) ORDER BY dist ASC LIMIT ' || SearchLimit;
-- Loop over this sample
   FOR result IN ( SELECT height::FLOAT,ST_ClosestPoint(st_setsrid(way,3857),st_setsrid(saddlepoint::geometry,3857)) AS cp,dist::FLOAT
                          FROM dblink('saddle_contours_connection',querystring) 
                               AS t1(way geometry,height integer,dist float)
                 ) LOOP
-- first contour line defines the "height" of the saddle point
    IF (i=1) THEN
     IF (ABS(saddleheight-result.height)>MinDescent) THEN
      SELECT CAST(d AS INTEGER) INTO thisdirection FROM (SELECT degrees(ST_Azimuth(saddlepoint,result.cp)) AS d) AS foo;
-- decreasing slope: the saddle directs to the closest point on contour line
-- increasing slope: it directs 90° to this point
      IF (result.height<saddleheight) THEN thisdirection:=(360+thisdirection)%180;    END IF;
      IF (result.height>saddleheight) THEN thisdirection:=(360+thisdirection+90)%180; END IF;
-- First choice is made by the first contour line
      IF(firstdistance<0) THEN
-- all other contour lines may do corrections to the first choice weighted with (distane of the first point/distance of this point)
-- Instead of correcting clockwise by 170° do it 10° anti-clockwise
       IF(diffdirection> 90) THEN diffdirection=180-diffdirection; END IF;
       IF(diffdirection<-90) THEN diffdirection=diffdirection+180; END IF;
       IF (direction<0) THEN direction:=direction+180; END IF;
      END IF;
     END IF;
    END IF;
   END LOOP getcontourloop;
-- don't close dblink-connection, we will need it again soon
-- PERFORM dblink_disconnect('saddle_contours_connection');
  RETURN direction;
$$ LANGUAGE plpgsql;