关于空间分析JTS的总结——筛点

筛点：往往库里返回的数据的点非常密集，筛点后会甩掉大量的较小偏移的临近点，并根据点与点之前距离的设定（例如：距离50米以内的点甩掉）和最大甩点数（例如：最多甩到10000个点就不甩了），减小精度来增加空间运算速度。

实例代码：

distanceToleranceMeter：50 --最小甩点距离

maxCoordinateCount：10000  --最大甩点数

 

@Override
    public <T> List<Coordinate> simplify(List<T> lngLatList, Function<T, Coordinate> transformer) {
        // 地图匹配最小距离 100m
        double distanceTolerance = GeometryUtil.getEarthArcDistance(distanceToleranceMeter);
        List<Coordinate> coordinates = Lists.newArrayList();

        Coordinate lastCoordinate = null;
        for (T lonLat : lngLatList) {
            // Longitude;Latitude;z,
            Coordinate coordinate = transformer.apply(lonLat);
            if (coordinate == null) {
                continue;
            }
            if (lastCoordinate == null || !coordinate.equals2D(lastCoordinate, 0.000001)) {
                coordinates.add(coordinate);
                lastCoordinate = coordinate;
            }
        }
        if (coordinates.isEmpty()) {
            return coordinates;
        }
        Coordinate[] pts = coordinates.toArray(new Coordinate[coordinates.size()]);
        coordinates.clear();
        double currentDistanceTolerance = distanceTolerance;
        do {
            // 精简点算法在参数【distanceTolerance】定值情况下，点不会再减少，故增加距离，避免死循环
            pts = DouglasPeuckerLineSimplifier.simplify(pts, currentDistanceTolerance);
            currentDistanceTolerance += GeometryUtil.getEarthArcDistance(10D);
        } while (pts.length > maxCoordinateCount);
        return Lists.newArrayList(pts);
    }

@Override
    public List<Coordinate> buildCoordinates(List<String> lngLatList, boolean inverseGeo) {
        List<Coordinate> coordinates  = simplify(lngLatList, new Function<String, Coordinate>() {
            public Coordinate apply(String coord) {
                try {
                    String[] arr = StringUtils.split(coord,";");
                    String longitude = arr[0];
                    String latitude = arr[1];
                    if (longitude != null && latitude != null) {
                        return new Coordinate(Double.parseDouble(longitude), Double.parseDouble(latitude));
                    }
                } catch (NumberFormatException e) {
                    logger.error(e.getMessage(), e);
                }
                return null;
            }
        });
        if(inverseGeo){//是否批量转偏移
            List<String[]> stringList = coordinates.stream().map(t -> new String[]{t.getX() + "", t.getY() + ""}).collect(Collectors.toList());
            List<String> result = mapService.inverseGeoConvert(stringList);
            coordinates = result.stream().map(t -> new Coordinate(Double.parseDouble(t.split(",")[0]), Double.parseDouble(t.split(",")[1]))).collect(Collectors.toList());
        }
        return coordinates;
    }