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从shp文件读取坐标并计算距离

geotools gis java

George · 技术社区 · 7 年前

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,我想计算距离的一个点是:

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

我知道要计算距离,我会做:

     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();

但我不知道如何找到目标点的坐标(ports.shp文件):

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

我有 features getCoordinates() 方法

而且,正如我所见 ports.shp 由许多 POINT 几何学我是否必须用参考点计算每个点,然后选择最近的点?

1 回复 | 直到 7 年前

Ian Turton 7 年前

功能具有 getDefaultGeometry

编辑

您的问题是单元不匹配,您正在设置 MinDist

我开始尝试通过限制初始搜索边界来提高搜索效率,但即使在使用填充位置数据集时,它也足够快,我真的不知道它是否有帮助。

    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());
}