场景
Java中使用JTS对空间几何计算(读取WKT、距离、点在面内、长度、面积、相交等)：
Java中使用JTS对空间几何计算(读取WKT、距离、点在面内、长度、面积、相交等)_jts-core_霸道流氓气质的博客-CSDN博客
Java+GeoTools实现WKT数据根据EPSG编码进行坐标系转换：
Java+GeoTools实现WKT数据根据EPSG编码进行坐标系转换_霸道流氓气质的博客-CSDN博客
基于gis的业务场景中，需要在地图中录入区域数据的wkt数据，然后根据某个坐标点判断是属于哪个区域，
以及距离所属区域中最近的端点的方位角，比如坐标点位于某区域东南方向100米。
注：
博客：
霸道流氓气质_C#,架构之路,SpringBoot-CSDN博客
实现
1、参考上面引入jts的依赖。
首先数据库中存储的所有线的WKT数据为
其中region_name为线的名称，region_wkt为线的wkt字符串。
首先从数据库中读取所有的wkt字符串数据，并转换为map类型数据方便处理以及赋值线的名称到linestring的userData字段。
List<LineString> regionList = new ArrayList<>();
Map<String, List<LineString>> regionMap = new HashMap<>();
//读取录入的区域位置信息
RegionManagement param = RegionManagement.builder().deleteFlag(false).build();
List<RegionManagement> regionManagements = regionManagementMapper.selectList(param);
for (RegionManagement regionManagement : regionManagements) {
LineString lineString = readWKT(regionManagement.getRegionWKT());
RegionDTO regionDTO = JSON.parseObject(JSON.toJSONString(regionManagement), RegionDTO.class);
regionDTO.setUpdateTime(regionManagement.getUpdateTime().toString());
lineString.setUserData(regionDTO);
regionList.add(lineString);
}
//将区域list流处理为map，方便快速查找
Map<String, List<RegionManagement>> collect = regionManagements.stream().collect(Collectors.groupingBy(RegionManagement::getRegionName));
for (String name : collect.keySet()) {
List<LineString> tmp = new ArrayList<>();
collect.get(name).forEach(item -> tmp.add(readWKT(item.getRegionWKT())));
regionMap.put(name, tmp);
}这里的RegionManagement用来读取数据库中存储的wkt字符串等数据，实现为
import com.fasterxml.jackson.annotation.JsonFormat;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;
import java.util.Date;
@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
public class RegionManagement {
private Long id;
private String regionName;
private String regionWKT;
// 0 false ; 1 true
private boolean deleteFlag;
@JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss")
private Date updateTime;
}调用读取wkt字符串并转换为jts的LineString对象的方法readWKT实现为
//读取wkt数据为LineString
public LineString readWKT(String regionWKT){
GeometryFactory fact = new GeometryFactory();
WKTReader reader = new WKTReader(fact);
LineString geometry1 = null;
try {
geometry1 = (LineString) reader.read(regionWKT);
} catch (ParseException e) {
e.printStackTrace();
}
return geometry1;
}中间获取所需要的数据的RegionDTO的实现为
import lombok.Data;
@Data
public class RegionDTO {
private Long id;
private String regionName;
private String updateTime;
}2、将要判断方位的坐标值声明为Point2D对象
//目标点位
Point2D.Double carPoint = new Point2D.Double(36582834.745, 4259820.7951);3、获取距离目标点位最近的线
//获取离目标点位最近的线
LineString lineString = findNearestLine(carPoint, 10D, regionList);这里调用的findNearestLine方法的实现
//查找最近的线，jts工具做线的缓冲区，扩展宽度为10
public LineString findNearestLine(java.awt.geom.Point2D.Double point, Double FuzzyLookupRange, List<LineString> lineStringList) {
Point a = createPoint(point.getX(), point.getY());
return lineStringList.parallelStream().filter((lineString) -> lineString.buffer(FuzzyLookupRange).contains(a)).min((o1, o2) -> {
Double ax = o1.distance(a);
Double axx = o2.distance(a);
return ax.compareTo(axx);
}).orElse(null);
}这里调用了createPoint用来创建point对象
//根据坐标x y创建点对象
public static Point createPoint(Double x, Double y) {
GeometryFactory a = JTSFactoryFinder.getGeometryFactory();
return a.createPoint(new Coordinate(x, y));
}然后使用lineString.buffer方法对线做缓冲区，扩展宽度为10，即将线向外扩充成类似区域的概念，判断点是否在扩充后
的区域内，如果有多个区域，则取距离最小的一个。
LineString.buffer方法的使用可参考：
Geometry (JTS Topology Suite 1.13 API) - Javadoc Extreme)
Computes a buffer area around this geometry having the given width. The buffer of a Geometry is the Minkowski sum or difference of the geometry
with a disc of radius abs(distance).
Mathematically-exact buffer area boundaries can contain circular arcs.
To represent these arcs using linear geometry they must be approximated with line segments.
The buffer geometry is constructed using 8 segments per quadrant to approximate the circular arcs. The end cap style is CAP_ROUND.
The buffer operation always returns a polygonal result. The negative or zero-distance buffer of lines and points is always an empty Polygon.
This is also the result for the buffers of degenerate (zero-area) polygons.
直译：
计算具有给定宽度的几何体周围的缓冲区。几何体的缓冲区是具有半径为abs（距离）的圆盘的几何体的Minkowski和或差。
数学上精确的缓冲区边界可以包含圆弧。要使用线性几何图形表示这些圆弧，必须使用线段对其进行近似。
缓冲区几何结构使用每个象限8个线段来近似圆弧。端盖样式为cap_ROUND。
缓冲区操作总是返回多边形结果。直线和点的负或零距离缓冲区始终为空多边形。
这也是退化（零面积）多边形缓冲区的结果。
然后获取距离最近的线的名称并输出
//获取离目标点位最近的线
LineString lineString = findNearestLine(carPoint, 10D, regionList);
String regionName = "区域位置为空";
if (lineString != null) {
RegionDTO userData = (RegionDTO) lineString.getUserData();
regionName = userData.getRegionName();
}
System.out.println(regionName);4、获取坐标点相对于该线的方位角
String azimuth;
if (!regionName.equals("区域位置为空")) {
List<LineString> lineStringList = regionMap.get(regionName);
LineString closeLine;
if (lineStringList.size() > 1) {
closeLine = findNearestLine(carPoint, 10D, lineStringList);
} else {
closeLine = lineStringList.get(0);
}
//获取线的两个端点
Point startPoint = closeLine.getStartPoint();
Point endPoint = closeLine.getEndPoint();
//获取点位到两个端点的距离
double startDistance = startPoint.distance(createPoint(carPoint.getX(), carPoint.getY()));
double endDistance = endPoint.distance(createPoint(carPoint.getX(), carPoint.getY()));
//获取较近的点作为参考点判断方位距离
if (startDistance <= endDistance) {
//获取方位角
azimuth = regionName + DirectionUtil.getAzimuth(startPoint.getX(), startPoint.getY(), carPoint.getX(), carPoint.getY()) + "方向路口" + BigDecimal.valueOf(startDistance).intValue() + "米";
} else {
azimuth = regionName + DirectionUtil.getAzimuth(endPoint.getX(), endPoint.getY(), carPoint.getX(), carPoint.getY()) + "方向路口" + BigDecimal.valueOf(endDistance).intValue() + "米";
}
} else {
azimuth = "[" + carPoint.getX() + "," + carPoint.getY() + "]";
}
System.out.println(azimuth);其中获取方位角的工具类DirectionUtil.getAzimuth实现
import org.locationtech.jts.geom.LineSegment;
public class DirectionUtil {
/**
* 笛卡尔坐标系
*/
enum DirectionEnum {
DUE_EAST("正东", "==0 || ==360"),
DUE_NORTHEAST("东北", "==45"),
DUE_NORTH("正北", "==90"),
NORTH_NORTHWEST("西北", "90<theta<135"),
DUE_WEST("正西", "==180"),
WEST_SOUTHWEST("西南", "180<theta<225"),
DUE_SOUTH("正南", "==270"),
DUE_SOUTHEAST("东南", "==315");
private String direction;
private String describe;
DirectionEnum(String direction, String describe) {
this.direction = direction;
this.describe = describe;
}
public String getDirection() {
return direction;
}
public void setDirection(String direction) {
this.direction = direction;
}
public String getDescribe() {
return describe;
}
public void setDescribe(String describe) {
this.describe = describe;
}
}
/**
* 获取方位角
*
* @param x1 观测点x
* @param y1 观测点y
* @param x2 目标点x
* @param y2 目标点y
* @return 返回距离观测点的方位角
*/
public static String getAzimuth(double x1, double y1, double x2, double y2) {
LineSegment lineSegment = new LineSegment(x1, y1, x2, y2);
double angle1 = lineSegment.angle();
double angle = Math.toDegrees(lineSegment.angle());
if (angle < 0) {
angle = angle + 360;
}
if ((0 < angle && angle < 12.5) || (347.5 < angle && angle < 360)) {
return DirectionEnum.DUE_EAST.getDirection();
} else if (12.5 < angle && angle < 77.5) {
return DirectionEnum.DUE_NORTHEAST.getDirection();
} else if (77.5 < angle && angle < 102.5) {
return DirectionEnum.DUE_NORTH.getDirection();
} else if (102.5 < angle && angle < 167.5) {
return DirectionEnum.NORTH_NORTHWEST.getDirection();
} else if (167.5 < angle && angle < 192.5) {
return DirectionEnum.DUE_WEST.getDirection();
} else if (192.5 < angle && angle < 257.5) {
return DirectionEnum.WEST_SOUTHWEST.getDirection();
} else if (257.5 < angle && angle < 282.5) {
return DirectionEnum.DUE_SOUTH.getDirection();
} else if (282.5 < angle && angle < 347.5) {
return DirectionEnum.WEST_SOUTHWEST.getDirection();
} else {
return "ERROR";
}
}
}逻辑就是对比目标点到线的两个端点的距离，取较近的进行判断，然后做方位角判断。
运行效果测试
