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Circle to Geometry conversion is highly inaccurate for GeoCircle #177

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hsbakshi opened this issue Mar 7, 2020 · 1 comment
Closed

Circle to Geometry conversion is highly inaccurate for GeoCircle #177

hsbakshi opened this issue Mar 7, 2020 · 1 comment

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@hsbakshi
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hsbakshi commented Mar 7, 2020

Problem: JtsShapeFactory has a 'getGeometryFrom' method that allows converting a Shape object to a Geometry object. This method can be used to transform a Circle to a Geometry (Polygon). This conversion currently returns a highly inaccurate result when

Test case:

@Test
public void testCircleGeometryConversions() {
  // Nunavat (Far North)
  circleGeometryConversionTest(-83.10, 70.30, 100);
}
                                                                                                             
private void circleGeometryConversionTest(double x, double y, double radiusKm) {
  Point circleCenter = new PointImpl(x, y, SpatialContext.GEO);
  double radiusDeg = DistanceUtils.dist2Degrees(radiusKm, DistanceUtils.EARTH_EQUATORIAL_RADIUS_KM);
  GeoCircle geoCircle = new GeoCircle(circleCenter, radiusDeg, SpatialContext.GEO);
                                                                                                             
  JtsShapeFactory shapeFactory = JtsSpatialContext.GEO.getShapeFactory();
  // Let's ensure the circle-to-polygon conversion is accurate accounting for geodesics.
  Geometry geometry = shapeFactory.getGeometryFrom(geoCircle);
  Assert.assertTrue(geometry instanceof Polygon);
  Polygon polygon = (Polygon) geometry;
  Coordinate[] coordinates = polygon.getExteriorRing().getCoordinates();
  int size = coordinates.length;
  Assert.assertTrue(size >= 100);
  GeodesicSphereDistCalc distCalc = new GeodesicSphereDistCalc.Haversine();
  for (Coordinate coordinate : coordinates) {
    // Check distance from center of each point
    Point point = new PointImpl(coordinate.x, coordinate.y, SpatialContext.GEO);
    double distance = distCalc.distance(point, circleCenter);
    double distanceKm = DistanceUtils.degrees2Dist(distance, DistanceUtils.EARTH_MEAN_RADIUS_KM);
    double expectedPrecision = radiusKm / 100;
    //Assert.assertEquals("Distance mismatch:  Point:" + point, radiusKm, distanceKm, expectedPrecision);
    System.out.println(String.format("Distance from point to center: %.2f km. Expected: %.2f km", distanceKm,
            radiusKm));
  }
}

Console output:
Distance from point to center: 99.91 km. Expected: 100.00 km
Distance from point to center: 101.04 km. Expected: 100.00 km
Distance from point to center: 105.10 km. Expected: 100.00 km
Distance from point to center: 111.72 km. Expected: 100.00 km
Distance from point to center: 120.40 km. Expected: 100.00 km
Distance from point to center: 130.60 km. Expected: 100.00 km
Distance from point to center: 141.86 km. Expected: 100.00 km
Distance from point to center: 153.78 km. Expected: 100.00 km
Distance from point to center: 166.06 km. Expected: 100.00 km
Distance from point to center: 178.45 km. Expected: 100.00 km
Distance from point to center: 190.76 km. Expected: 100.00 km
Distance from point to center: 202.81 km. Expected: 100.00 km
Distance from point to center: 214.49 km. Expected: 100.00 km
Distance from point to center: 225.66 km. Expected: 100.00 km
Distance from point to center: 236.24 km. Expected: 100.00 km
Distance from point to center: 246.15 km. Expected: 100.00 km
Distance from point to center: 255.32 km. Expected: 100.00 km
Distance from point to center: 263.67 km. Expected: 100.00 km
Distance from point to center: 271.16 km. Expected: 100.00 km
Distance from point to center: 277.75 km. Expected: 100.00 km
Distance from point to center: 283.38 km. Expected: 100.00 km
Distance from point to center: 288.04 km. Expected: 100.00 km
Distance from point to center: 291.69 km. Expected: 100.00 km
Distance from point to center: 294.31 km. Expected: 100.00 km
Distance from point to center: 295.89 km. Expected: 100.00 km
Distance from point to center: 296.42 km. Expected: 100.00 km
Distance from point to center: 295.89 km. Expected: 100.00 km
Distance from point to center: 294.31 km. Expected: 100.00 km
Distance from point to center: 291.69 km. Expected: 100.00 km
Distance from point to center: 288.04 km. Expected: 100.00 km
Distance from point to center: 283.38 km. Expected: 100.00 km
Distance from point to center: 277.75 km. Expected: 100.00 km
Distance from point to center: 271.16 km. Expected: 100.00 km
Distance from point to center: 263.67 km. Expected: 100.00 km
Distance from point to center: 255.32 km. Expected: 100.00 km
Distance from point to center: 246.15 km. Expected: 100.00 km
Distance from point to center: 236.24 km. Expected: 100.00 km
Distance from point to center: 225.66 km. Expected: 100.00 km
Distance from point to center: 214.49 km. Expected: 100.00 km
Distance from point to center: 202.81 km. Expected: 100.00 km
Distance from point to center: 190.76 km. Expected: 100.00 km
Distance from point to center: 178.45 km. Expected: 100.00 km
Distance from point to center: 166.06 km. Expected: 100.00 km
Distance from point to center: 153.78 km. Expected: 100.00 km
Distance from point to center: 141.86 km. Expected: 100.00 km
Distance from point to center: 130.60 km. Expected: 100.00 km
Distance from point to center: 120.40 km. Expected: 100.00 km
Distance from point to center: 111.72 km. Expected: 100.00 km
Distance from point to center: 105.10 km. Expected: 100.00 km
Distance from point to center: 101.04 km. Expected: 100.00 km
Distance from point to center: 99.91 km. Expected: 100.00 km
Distance from point to center: 101.84 km. Expected: 100.00 km
Distance from point to center: 106.61 km. Expected: 100.00 km
Distance from point to center: 113.80 km. Expected: 100.00 km
Distance from point to center: 122.89 km. Expected: 100.00 km
Distance from point to center: 133.35 km. Expected: 100.00 km
Distance from point to center: 144.74 km. Expected: 100.00 km
Distance from point to center: 156.69 km. Expected: 100.00 km
Distance from point to center: 168.93 km. Expected: 100.00 km
Distance from point to center: 181.21 km. Expected: 100.00 km
Distance from point to center: 193.36 km. Expected: 100.00 km
Distance from point to center: 205.22 km. Expected: 100.00 km
Distance from point to center: 216.67 km. Expected: 100.00 km
Distance from point to center: 227.62 km. Expected: 100.00 km
Distance from point to center: 237.96 km. Expected: 100.00 km
Distance from point to center: 247.62 km. Expected: 100.00 km
Distance from point to center: 256.54 km. Expected: 100.00 km
Distance from point to center: 264.67 km. Expected: 100.00 km
Distance from point to center: 271.95 km. Expected: 100.00 km
Distance from point to center: 278.34 km. Expected: 100.00 km
Distance from point to center: 283.80 km. Expected: 100.00 km
Distance from point to center: 288.31 km. Expected: 100.00 km
Distance from point to center: 291.84 km. Expected: 100.00 km
Distance from point to center: 294.38 km. Expected: 100.00 km
Distance from point to center: 295.91 km. Expected: 100.00 km
Distance from point to center: 296.42 km. Expected: 100.00 km
Distance from point to center: 295.91 km. Expected: 100.00 km
Distance from point to center: 294.38 km. Expected: 100.00 km
Distance from point to center: 291.84 km. Expected: 100.00 km
Distance from point to center: 288.31 km. Expected: 100.00 km
Distance from point to center: 283.80 km. Expected: 100.00 km
Distance from point to center: 278.34 km. Expected: 100.00 km
Distance from point to center: 271.95 km. Expected: 100.00 km
Distance from point to center: 264.67 km. Expected: 100.00 km
Distance from point to center: 256.54 km. Expected: 100.00 km
Distance from point to center: 247.62 km. Expected: 100.00 km
Distance from point to center: 237.96 km. Expected: 100.00 km
Distance from point to center: 227.62 km. Expected: 100.00 km
Distance from point to center: 216.67 km. Expected: 100.00 km
Distance from point to center: 205.22 km. Expected: 100.00 km
Distance from point to center: 193.36 km. Expected: 100.00 km
Distance from point to center: 181.21 km. Expected: 100.00 km
Distance from point to center: 168.93 km. Expected: 100.00 km
Distance from point to center: 156.69 km. Expected: 100.00 km
Distance from point to center: 144.74 km. Expected: 100.00 km
Distance from point to center: 133.35 km. Expected: 100.00 km
Distance from point to center: 122.89 km. Expected: 100.00 km
Distance from point to center: 113.80 km. Expected: 100.00 km
Distance from point to center: 106.61 km. Expected: 100.00 km
Distance from point to center: 101.84 km. Expected: 100.00 km
Distance from point to center: 99.91 km. Expected: 100.00 km
hsbakshi added a commit to hsbakshi/spatial4j that referenced this issue Mar 7, 2020
@hsbakshi
Improve conversion of GeoCircle to Shape(Polygon)
e3e5123 
Details of the problem are explained here: locationtech#177

The new test-case fails without the code change and passes after the code change.
hsbakshi added a commit to hsbakshi/spatial4j that referenced this issue Mar 7, 2020
@hsbakshi
Improve conversion of GeoCircle to Shape(Polygon)
677b43e 
Details of the problem are explained here: locationtech#177

The new test-case fails without the code change and passes after the code change.
@hsbakshi hsbakshi mentioned this issue Mar 7, 2020
Closed
hsbakshi added a commit to hsbakshi/spatial4j that referenced this issue Mar 8, 2020
@hsbakshi
Improve conversion of GeoCircle to Shape(Polygon)
a860205 
Details of the problem are explained here: locationtech#177

The new test-case fails without the code change and passes after the code change.
@hsbakshi hsbakshi mentioned this issue Mar 8, 2020
Closed
hsbakshi added a commit to hsbakshi/spatial4j that referenced this issue Mar 8, 2020
@hsbakshi
Improve conversion of GeoCircle to Shape(Polygon)
ec702cd 
Details of the problem are explained here: locationtech#177

The new test-case fails without the code change and passes after the code change.

Signed-off-by: Hrishi Bakshi <hrishi@amazon.com>
@hsbakshi hsbakshi mentioned this issue Mar 8, 2020
Merged
dsmiley pushed a commit that referenced this issue Mar 9, 2020
@hsbakshi @dsmiley
Improve conversion of GeoCircle to Shape(Polygon)
c9c36a0 
Details of the problem are explained here: #177

The new test-case fails without the code change and passes after the code change.

Signed-off-by: Hrishi Bakshi <hrishi@amazon.com>
@dsmiley
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dsmiley commented Mar 9, 2020

Thanks for contributing!

@dsmiley dsmiley closed this as completed Mar 9, 2020
abrokenjester pushed a commit to abrokenjester/spatial4j that referenced this issue Mar 12, 2020
@hsbakshi @abrokenjester
Improve conversion of GeoCircle to Shape(Polygon)
e231023 
Details of the problem are explained here: locationtech#177

The new test-case fails without the code change and passes after the code change.

Signed-off-by: Hrishi Bakshi <hrishi@amazon.com>
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@hsbakshi @dsmiley