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,我要从中计算距离的一点是：
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(?????));
我具有加载文件的功能,但没有任何getCoordinates()方法.
另外,正如我所见,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,然后选择最近的点？
解决方法:
功能部件具有getDefaultGeometry方法,该方法将为您提供所需的点.然后,您可以从该点获取坐标.
编辑
您的问题是单位不匹配,您将MinDist设置为边界框的宽度(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());
}
标签：java,gis,geotools 来源： https://codeday.me/bug/20191012/1901859.html
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