I noticed some inconsistency on geographies between ST_Project and ST_Segmentize in postgis when dealing with trying to segmentize over very long distances (around 18000-19000 km)
Below are two plpgsql functions that should give about the same result but they don't. I tried it using different versions of Postgis (up to 2.1.8).
For both functions I use a start point lat and long, an azimuth, a total length and a segment length.
CREATE OR REPLACE FUNCTION segmentize_line_manually(startLat DECIMAL, startLong DECIMAL, azimuth DECIMAL, max_distance_meter INT, interval_meter INT)RETURNS geometry AS$$DECLARE line_points geometry[]; startPoint geography := ST_MakePoint(startLong, startLat); distance_meter INT := 0; i INT := 1;BEGIN WHILE distance_meter < max_distance_meter LOOP distance_meter := distance_meter + interval_meter; line_points = geometry(ST_Project(startPoint, distance_meter, azimuth)); --RAISE INFO 'distance:% %', distance_meter, st_astext(line_points); i := i + 1; END LOOP; RETURN ST_MakeLine(line_points);END;$$LANGUAGE 'plpgsql' IMMUTABLE;CREATE OR REPLACE FUNCTION segmentize_line_auto(startLat DECIMAL, startLong DECIMAL, azimuth DECIMAL, max_distance_meter INT, interval_meter INT)RETURNS geometry AS$$DECLARE line_points geometry[]; azimuth_line geometry;BEGIN line_points[1] := geography(ST_MakePoint(startLong, startLat)); line_points[2] := ST_Project(line_points[1], max_distance_meter, azimuth); azimuth_line := ST_MakeLine(line_points); RETURN st_segmentize(geography(azimuth_line), interval_meter);END;$$LANGUAGE 'plpgsql' IMMUTABLE;I call both methods using the following parameters:
SELECT segmentize_line_****(0, 0, 0.628973508651991, 19000000, 50000);Is there a problem with my code, or is it really an issue with ST_Segmentize?
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Below are two plpgsql functions that should give about the same result but they don't. I tried it using different versions of Postgis (up to 2.1.8).
For both functions I use a start point lat and long, an azimuth, a total length and a segment length.
- segmentize_line_manually: I project the starting point at incremented distances (segment length) with the given azimuth using ST_Project.
- segmentize_line_auto: I project the starting point at the total distance with the given azimuth, then I call ST_Segmentize with the segment length.
CREATE OR REPLACE FUNCTION segmentize_line_manually(startLat DECIMAL, startLong DECIMAL, azimuth DECIMAL, max_distance_meter INT, interval_meter INT)RETURNS geometry AS$$DECLARE line_points geometry[]; startPoint geography := ST_MakePoint(startLong, startLat); distance_meter INT := 0; i INT := 1;BEGIN WHILE distance_meter < max_distance_meter LOOP distance_meter := distance_meter + interval_meter; line_points = geometry(ST_Project(startPoint, distance_meter, azimuth)); --RAISE INFO 'distance:% %', distance_meter, st_astext(line_points); i := i + 1; END LOOP; RETURN ST_MakeLine(line_points);END;$$LANGUAGE 'plpgsql' IMMUTABLE;CREATE OR REPLACE FUNCTION segmentize_line_auto(startLat DECIMAL, startLong DECIMAL, azimuth DECIMAL, max_distance_meter INT, interval_meter INT)RETURNS geometry AS$$DECLARE line_points geometry[]; azimuth_line geometry;BEGIN line_points[1] := geography(ST_MakePoint(startLong, startLat)); line_points[2] := ST_Project(line_points[1], max_distance_meter, azimuth); azimuth_line := ST_MakeLine(line_points); RETURN st_segmentize(geography(azimuth_line), interval_meter);END;$$LANGUAGE 'plpgsql' IMMUTABLE;I call both methods using the following parameters:
SELECT segmentize_line_****(0, 0, 0.628973508651991, 19000000, 50000);Is there a problem with my code, or is it really an issue with ST_Segmentize?
أكثر...