GeoTools Java – Measuring Distance Between Two Points Using GeoTools Java Library

geotools

I am using GeoTools to convert X and Y coordinates into points and get the distance between two points. I know that my coordinates are EPSG:32630 Name:WGS 84 / UTM zone 30N (https://epsg.io/32630). Then I created this small test to check the distance between two points. I am not sure if I am converting the X and Y coordinates correctly. And when I transform it to Points it throws an exception.

    Coordinate coordRad01 = new Coordinate(729664.353, 4373064.801);
    Coordinate coordRad02 = new Coordinate(730021.116, 4373070.406);
    Coordinate coordPoi01 = null;
    Coordinate coordPoi02 = null;
    MathTransform transformRadiusToPoint;
    try {
        CoordinateReferenceSystem radiusCRS = CRS.decode("EPSG:32630", true);
        CoordinateReferenceSystem pointCRS = CRS.decode("EPSG:4326", true);

        DirectPosition dp01 = JTS.toDirectPosition(coordRad01, radiusCRS);
        DirectPosition dp02 = JTS.toDirectPosition(coordRad02, radiusCRS);
        System.out.println("DirectPosition dp01: " + dp01 + " dp02: " + dp02);

        Double distance = JTS.orthodromicDistance(coordRad01, coordRad02, radiusCRS);
        System.out.println("Distance: " + distance + " meters");

        transformRadiusToPoint = CRS.findMathTransform(pointCRS, radiusCRS);
        coordPoi01 = JTS.transform(coordRad01, coordPoi01, transformRadiusToPoint);
        coordPoi02 = JTS.transform(coordRad02, coordPoi02, transformRadiusToPoint);

        distance = JTS.orthodromicDistance(coordPoi01, coordPoi02, pointCRS);
        System.out.println("Distance: " + distance + " meters");
    } catch (NoSuchAuthorityCodeException e) {
        e.printStackTrace();
    } catch (FactoryException e) {
        e.printStackTrace();
    } catch (TransformException e) {
        e.printStackTrace();
    }

error:

DirectPosition dp01: JTS.[729664.353, 4373064.801] dp02: JTS.[730021.116, 4373070.406]
Distance: 356.7176800591084 meters
Jul 23, 2019 12:40:26 PM org.geotools.referencing.operation.projection.TransverseMercator transform
WARNING: Possible use of "Transverse_Mercator" projection outside its valid area.
Longitude 729304°21.2'E is out of range (±180°).
Latitude 4372704°48.0'N is out of range (±90°).
Exception in thread "main" java.lang.IllegalArgumentException: Longitude 5449761°17.2'E is out of range (±180°).
    at org.geotools.referencing.GeodeticCalculator.checkLongitude(GeodeticCalculator.java:406)
    at org.geotools.referencing.GeodeticCalculator.setStartingGeographicPoint(GeodeticCalculator.java:549)
    at org.geotools.referencing.GeodeticCalculator.setStartingPosition(GeodeticCalculator.java:591)
    at org.geotools.geometry.jts.JTS.orthodromicDistance(JTS.java:635)
    at org.sense.flink.pojo.Point.main(Point.java:105)

Best Answer

TLDR; You have your transform backwards, you want to go from transverse mercator to WGS84 so it needs to be:

transformRadiusToPoint = CRS.findMathTransform(radiusCRS, pointCRS);

But you shouldn't need to convert to a geographic projection just to get the distance if your points are already in a planar/projected projection (CRS). I would simply use Pythagoras:

double d = Math.sqrt((coordRad01.x - coordRad02.x) * (coordRad01.x - coordRad02.x)
    + (coordRad01.y - coordRad02.y) * (coordRad01.y - coordRad02.y));

This then gives:

d=356.8070265480071
DirectPosition dp01: JTS.[729664.353, 4373064.801] dp02: JTS.[730021.116, 4373070.406]
Distance: 356.71768006444 meters
Distance: 356.71768006444 meters

Which all agree nicely.

Related Solutions

GeoTools Linestring – Calculating Distance in Meters

Using the following code I can get an answer of 38355.3256m (which is probably close enough) - I imagine that with a more careful choice of central point a more "accurate" result might be obtained.

    Geometry g1 = reader.read("LINESTRING(13.45 52.47,13.46 52.48)");
    Geometry g2 = reader.read("LINESTRING(13.00 52.00,13.1 52.2)");
    System.out.println(g1.distance(g2));
    CoordinateReferenceSystem auto = CRS.decode("AUTO:42001,13.45,52.3");
    System.out.println(auto);
    MathTransform transform = CRS.findMathTransform(DefaultGeographicCRS.WGS84,
            auto);
    Geometry g3 = JTS.transform(g1, transform);
    Geometry g4 = JTS.transform(g2, transform);
    System.out.println(g3.distance(g4));

[GIS] Finding distance in meters between point and path in lat/lon using GeoTools

The code from the previous question does in fact solve this problem once you have explored the issue a bit.

Basically your line doesn't have enough points so it "cuts" the corner across the more localised projection that is used to allow JTS to proceed as if the Earth is flat. This needs one additional line of code:

route = (LineString) Densifier.densify(route, .01);

The brown line is your original 3 point line and the blue line is a densified line (that has points added so it projects properly), shown in a local projection (EPSG:2470). As you can see the distance to the brown line to the point is much shorter than it should be.

So here is some suitably modified code:

public double getDistance(Point point, LineString line) {
double dist = -1.0;
try {
  String code = "AUTO:42001," + point.getX() + "," + point.getY();
  CoordinateReferenceSystem auto = CRS.decode(code);
  // auto = CRS.decode("epsg:2470");
  MathTransform transform = CRS.findMathTransform(DefaultGeographicCRS.WGS84, auto);
  Geometry g3 = JTS.transform(line, transform);
  Geometry g4 = JTS.transform(point, transform);

  Coordinate[] c = DistanceOp.nearestPoints(g4, g3);

  Coordinate c1 = new Coordinate();
  //System.out.println(c[1].distance(g4.getCoordinate()));
  JTS.transform(c[1], c1, transform.inverse());
  //System.out.println(geometryFactory.createPoint(c1));
  dist = JTS.orthodromicDistance(point.getCoordinate(), c1, DefaultGeographicCRS.WGS84);
} catch (Exception e) {
  e.printStackTrace();
}
return dist;

}

And incase you are wondering about the difference between the "flat distance" (c[1].distance(g4.getCoordinate())) is 760.731km and the "curved distance" (JTS.orthodromicDistance(point.getCoordinate(), c1, DefaultGeographicCRS.WGS84);) is 760.980km. For reference the distance tool in QGIS gives 760.919 km.

Best Answer

Related Solutions

GeoTools Linestring – Calculating Distance in Meters

[GIS] Finding distance in meters between point and path in lat/lon using GeoTools

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