Question

我想计算从自然地球数据到点到shp文件（ports.shp）的最近距离。

例如，我正在加载文件的功能：

/* For mobile phones: */
.your-font-class {
    font-size: 0.5 em
}

@media only screen and (min-width: 500px) {
    /* For desktop: */
    .your-font-class {
        font-size: 1em
    }
}

}

现在，我想要计算距离的一点是：

...
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();

我知道要计算我将要做的距离：

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

但我不知道如何找到目标点的坐标（ports.shp文件）：

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();

我有加载文件的Point dest = gf.createPoint(new Coordinate(?????));，但它没有任何features方法。

另外，我可以看到getCoordinates()由许多ports.shp几何组成。我是否必须以某种方式计算每个点与参考点然后选择最近的？

Answer 1

功能有一个getDefaultGeometry方法，可以为您提供所需的点。然后你可以从这个点获得坐标。

修改

您的问题是单位不匹配，您将MinDist设置为边界框的宽度（以度为单位，因此大约为360），但将其与以米为单位的距离（约为7800000）进行比较，因此您从未找到过点足够接近保存。

我开始尝试通过限制初始搜索范围来提高搜索效率，但即使使用填充的地点数据集也是如此，我无法确定它是否有用。

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()); }

从shp文件中读取坐标并计算距离

1 个答案: