使用JAVA中的geotools从定义距离(km)内的线(GPS坐标

问题描述

使用 geotools 是否有可能从定义距离内的线 (coords[]) 生成多边形?例如.(100,100), (101,100), (102,100) 距离 1 公里.所以从每一点它生成一个圆圈并变成某事.喜欢:

With geotools would it be possible that generating a polygon from a line (coords[]) in a defined distance? E.g. (100,100), (101,100), (102,100) with distance 1km. So from each point it generates a circle and becomes sth. like:

-------------之前

-------------- before

(========) 之后

(========) after

或者我必须先将 GPS 坐标转换为以 km 为单位的正交坐标，然后使用三角函数生成多边形，最后再将其转换回 GPS?

Or I have to firstly convert GPS coordinates into orthogonal coordinates in km, and then generating a polygon using Trigonometric functions, and finally, convert it back into GPS?

推荐答案

最简单的方法是调用底层 JTS 几何的 buffer(distance) 方法.棘手的一点是处理与以米为单位的投影之间的重投影(因此您可以以米或公里为单位指定缓冲区).

At it's simplest you simply need to call the buffer(distance) method on the underlying JTS geometry. The tricky bit is handling the reprojection to and from a projection which is in meters (so you can specify your buffer in meters or kilometers).

public SimpleFeature bufferFeature(SimpleFeature feature,
        Measure<Double, Length> distance) {
    // extract the geometry
    GeometryAttribute gProp = feature.getDefaultGeometryProperty();
    CoordinateReferenceSystem origCRS = gProp.getDescriptor()
        .getCoordinateReferenceSystem();

    Geometry geom = (Geometry) feature.getDefaultGeometry();
    Geometry pGeom = geom;
    MathTransform toTransform,fromTransform = null;
    // reproject the geometry to a local projection
    if (!(origCRS instanceof ProjectedCRS)) {

        Point c = geom.getCentroid();
        double x = c.getCoordinate().x;
        double y = c.getCoordinate().y;

        String code = "AUTO:42001," + x + "," + y;
        // System.out.println(code);
        CoordinateReferenceSystem auto;
        try {
        auto = CRS.decode(code);
         toTransform = CRS.findMathTransform(
            DefaultGeographicCRS.WGS84, auto);
         fromTransform = CRS.findMathTransform(auto,
            DefaultGeographicCRS.WGS84);
        pGeom = JTS.transform(geom, toTransform);
        } catch (MismatchedDimensionException | TransformException
            | FactoryException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
        }

    }

    // buffer
    Geometry out = buffer(pGeom, distance.doubleValue(SI.METER));
    Geometry retGeom = out;
    // reproject the geometry to the original projection
    if (!(origCRS instanceof ProjectedCRS)) {
        try {
        retGeom = JTS.transform(out, fromTransform);
        } catch (MismatchedDimensionException | TransformException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
        }
    }
    // return a new feature containing the geom
    SimpleFeatureType schema = feature.getFeatureType();
    SimpleFeatureTypeBuilder ftBuilder = new SimpleFeatureTypeBuilder();
    ftBuilder.setCRS(origCRS);
    //ftBuilder.setDefaultGeometry("buffer");
    ftBuilder.addAll(schema.getAttributeDescriptors());
    ftBuilder.setName(schema.getName());

    SimpleFeatureType nSchema = ftBuilder.buildFeatureType();
    SimpleFeatureBuilder builder = new SimpleFeatureBuilder(nSchema);
     List<Object> atts = feature.getAttributes();
     for(int i=0;i<atts.size();i++) {
         if(atts.get(i) instanceof Geometry) {
         atts.set(i, retGeom);
         }
     }
    SimpleFeature nFeature = builder.buildFeature(null, atts.toArray() );
    return nFeature;
    }

完整代码在 https://gist.github.com/ianturton/9a7cfee378e7072ec3cd这显示了如何处理整个事情.

The full code is at https://gist.github.com/ianturton/9a7cfee378e7072ec3cd which shows how to handle the whole thing.

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