从shp文件读取坐标并计算距离
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？
回答：
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。
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());
}
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