Geotools: bounding box for a buffer in wgs84

问题:

I am need a Java function that will generate a bounding box (rectangle) around a buffer. The buffer is defined by the center point (WGS84 coordinate) and the radius (in meters).

Getting a bounding box for a buffer in JTS seems to be quite simple:

Point center = .... Geometry boundingBox = center.buffer(...).getEnvelope(); 

This however is pure planar geometry. Is there a way to do this using a coordinate reference system with the distance given in meters?

Optimally with Geotools but other Java solutions will also work...

回答1:

I ended up using a GeodeticCalculator to manually find the corners of the box. Frankly the results aren't very precise, but that's the best solution I found till now:

 GeometryFactory geometryFactory = JTSFactoryFinder.getGeometryFactory();  CoordinateReferenceSystem wgs84 = DefaultGeographicCRS.WGS84;  GeodeticCalculator geodeticCalculator = new GeodeticCalculator(wgs84);  geodeticCalculator.setStartingGeographicPoint(center.getX(), center.getY());  Coordinate[] coordinates = new Coordinate[5];  for (int i = 0; i < 4; i++) {     geodeticCalculator.setDirection(-180 + i * 90 + 45, bufferRadiusMeters * Math.sqrt(2));     Point2D point2D = geodeticCalculator.getDestinationGeographicPoint();     coordinates[i] = new Coordinate(point2D.getX(), point2D.getY());  }  coordinates[4] = coordinates[0];  Polygon box = geometryFactory.createPolygon(coordinates); 

回答2:

Although you have approached it in another way, I have another solution for that. The results will be way more precise than with your proposed solution.

GeometryFactory GEOMETRY_FACTORY = JTSFactoryFinder.getGeometryFactory();  // Remember, order is (longitude, latitude) Coordinate center = Coordinate(2.29443, 48.85816); Point point = GEOMETRY_FACTORY.createPoint(center);  // Buffer 50KM around the point, then get the envelope Envelope envelopeInternal = buffer(point, 50000).getEnvelopeInternal();  // Then you can play with the envelope, e.g., double minX = envelopeInternal.getMinX(); double maxX = envelopeInternal.getMaxX();  // The buffer using distanceInMeters private Geometry buffer(Geometry geometry, double distanceInMeters) throws FactoryException, TransformException {      String code = "AUTO:42001," + geometry.getCentroid().getCoordinate().x + "," + geometry.getCentroid().getCoordinate().y;      CoordinateReferenceSystem auto = CRS.decode(code);       MathTransform toTransform = CRS.findMathTransform(DefaultGeographicCRS.WGS84, auto);      MathTransform fromTransform = CRS.findMathTransform(auto, DefaultGeographicCRS.WGS84);       Geometry pGeom = JTS.transform(geometry, toTransform);      Geometry pBufferedGeom = pGeom.buffer(distanceInMeters);      return JTS.transform(pBufferedGeom, fromTransform); } 

And here is the map with the result, buffer in red, envelope in black.

回答3:

Here is a simple solution that I used to generate bounding box coordinates that I use with GeoNames citieJSON API to get nearby big cities from a gps decimal coordinate.

This is a Java method from my GitHub repository: FusionTableModifyJava

I had a decimal GPS location and I needed to find the biggest city/state "near" that location. I needed a relatively accurate bounding box to pass to the citiesJSON GeoNames webservice to get back the biggest city in that bounding box. I pass the location and the "radius" I am interested in (in km) and it gives back the north, south, east, west decimal coordinates needed to pass to citiesJSON.

(I found these resources useful in doing my research:

Calculate distance, bearing and more between Latitude/Longitude points.

Longitude - Wikipedia)

It is not super accurate but accurate enough for what I was using it for:

    // Compute bounding Box coordinates for use with Geonames API.     class BoundingBox     {         public double north, south, east, west;         public BoundingBox(String location, float km)         {              //System.out.println(location + " : "+ km);             String[] parts = location.replaceAll("\\s","").split(","); //remove spaces and split on ,              double lat = Double.parseDouble(parts[0]);             double lng = Double.parseDouble(parts[1]);              double adjust = .008983112; // 1km in degrees at equator.             //adjust = 0.008983152770714983; // 1km in degrees at equator.              //System.out.println("deg: "+(1.0/40075.017)*360.0);               north = lat + ( km * adjust);             south = lat - ( km * adjust);              double lngRatio = 1/Math.cos(Math.toRadians(lat)); //ratio for lng size             //System.out.println("lngRatio: "+lngRatio);              east = lng + (km * adjust) * lngRatio;             west = lng - (km * adjust) * lngRatio;         }      } 

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