問題描述

使用 geotools 是否有可能從定義距離內的線 (coords[]) 生成多邊形?例如.(100,100), (101,100), (102,100) 距離 1 公里.所以從每一點它生成一個圓圈并變成某事.喜歡:

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

或者我必須先將 GPS 坐標轉換為以 km 為單位的正交坐標，然后使用三角函數生成多邊形，最后再將其轉換回 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?

推薦答案

最簡單的方法是調用底層 JTS 幾何的 buffer(distance) 方法.棘手的一點是處理與以米為單位的投影之間的重投影(因此您可以以米或公里為單位指定緩沖區).

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;
    }

完整代碼在 https://gist.github.com/ianturton/9a7cfee378e7072ec3cd這顯示了如何處理整個事情.

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

這篇關于使用JAVA中的geotools從定義距離(km)內的線(GPS坐標)生成多邊形的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！