从shp文件读取坐标并计算距离

Question

我想根据自然地球数据计算一个点到一个shp文件（ports.shp）的最近距离。

例如，我正在加载文件的功能：

...
String filename = "10m_cultural/ne_10m_ports.shp";
...


 public static void Calcs(String filename) 
    throws IOException, NoSuchAuthorityCodeException, FactoryException, TransformException {

    HashMap<String, Object> params = new HashMap<>();
    params.put("url", DataUtilities.fileToURL(new File(filename)));
    DataStore ds = DataStoreFinder.getDataStore(params);

    String name = ds.getTypeNames()[0];
    SimpleFeatureSource source = ds.getFeatureSource(name);
    SimpleFeatureCollection features = source.getFeatures();

}

现在，例如要计算距离的一点是：

GeometryFactory gf = JTSFactoryFinder.getGeometryFactory();
Point p = gf.createPoint(new Coordinate(43, 18));

我知道要计算距离，我会这样做：

     CoordinateReferenceSystem crs = CRS.decode("EPSG:4326");


      Point start = gf.createPoint(new Coordinate(43, 18));
      Point dest = gf.createPoint(new Coordinate(?????));

      GeodeticCalculator gc = new GeodeticCalculator(crs);
      gc.setStartingPosition(JTS.toDirectPosition(start.getCoordinate(), crs));
      gc.setDestinationPosition(JTS.toDirectPosition(dest.getCoordinate(), crs));


      double distance = gc.getOrthodromicDistance();

但是我不知道如何找到目的地的坐标（ports.shp文件）：

Point dest = gf.createPoint(new Coordinate(?????));

我有features从加载文件，但它没有任何getCoordinates()方法。

而且，正如我所见，它ports.shp由许多POINT几何组成。我是否必须以某种方式计算参考点的每个点，然后选择最接近的点？

Answer 1

功能部件具有一种getDefaultGeometry可以为您提供所需要点的方法。然后，您可以从该点获取坐标。

编辑

您的问题是单位不匹配，您MinDist将边界框的宽度设置为度（以度为单位，大约为360），但将其与以米为单位的距离（大约为7800000）进行比较，因此您找不到一个足以保存的点。

我开始通过限制初始搜索范围来提高搜索效率，但是即使使用了我无法确定是否有效的填充位置数据集，它也足够快。

    final double MAX_SEARCH_DISTANCE = Math.max(index.getBounds().getWidth(), index.getBounds().getHeight());
    double searchDist = 0.01;

    while (searchDist < MAX_SEARCH_DISTANCE) {
        // start point (user input)
        Coordinate coordinate = p.getCoordinate();

        ReferencedEnvelope search = new ReferencedEnvelope(new Envelope(coordinate),
                index.getSchema().getCoordinateReferenceSystem());

        search.expandBy(searchDist);
        BBOX bbox = ff.bbox(ff.property(index.getSchema().getGeometryDescriptor().getName()), (BoundingBox) search);
        SimpleFeatureCollection candidates = index.subCollection(bbox);

        double minDist = Double.POSITIVE_INFINITY; // can't use
                                                    // MAX_Search_dist here
                                                    // as it is degrees and
                                                    // dists are meters
        Coordinate minDistPoint = null;
        double dist = 0;
        Point dest = null;
        SimpleFeatureIterator itr = candidates.features();
        CoordinateReferenceSystem crs = DefaultGeographicCRS.WGS84;
        try {
            SimpleFeature feature = null;
            while (itr.hasNext()) {
                feature = itr.next();

                // destination point
                dest = (Point) feature.getDefaultGeometry();
                GeodeticCalculator gc = new GeodeticCalculator(crs);
                gc.setStartingPosition(JTS.toDirectPosition(p.getCoordinate(), crs));
                gc.setDestinationPosition(JTS.toDirectPosition(dest.getCoordinate(), crs));
                // Calculate distance between points
                dist = gc.getOrthodromicDistance();
                // System.out.println(feature.getID()+": "+dist);
                if (dist < minDist) {
                    minDist = dist;
                    minDistPoint = dest.getCoordinate();
                    lastMatched = feature;
                }
            }

        } finally {
            itr.close();
        }
        Point ret = null;

        if (minDistPoint == null) {
            searchDist *= 2.0;
            System.out.println("repeat search");
        } else {
            ret = gf.createPoint(minDistPoint);
            return ret;
        }
    }
    return gf.createPoint(new Coordinate());
}