空间数据模型
(1)、JTS Geometry model
(2)、ISO Geometry model (Geometry Plugin and JTS Wrapper Plugin)
GeoTools has two implementations of these interfaces:
Geometry Plugin a port of JTS 1.7 to the ISO Geometry interfaces
JTS Wrapper Plugin an implementation that delegates all the work to JTS
JTS包结构
系（linearref包）、计算交点（noding包）、几何图形操作（operation包）、平面图（planargraph包）、多边形化（polygnize包）、精度（precision）、工具（util包）重点理解JTS Geometry model
(1) JTS提供了如下的空间数据类型
Point
MultiPoint
LineString
LinearRing 封闭的线条
MultiLineString 多条线
Polygon
MultiPolygon
GeometryCollection 包括点，线，面
(2) 支持接口
Coordinate
Coordinate（坐标）是用来存储坐标的轻便的类。它不同于点，点是Geometry的子类。不像模范Point的对象（包含额外的信息，例如一个信包，一个精确度模型和空间参考系统信息），Coordinate只包含纵座标值和存取方法。
Envelope(矩形)
一个具体的类，包含一个最大和最小的x 值和y 值。
GeometryFactory
GeometryFactory提供一系列的有效方法用来构造来自Coordinate类的Geometry对象。
Example
package com.mapbar.geo.jts;
import org.geotools.geometry.jts.JTSFactoryFinder;
import com.vividsolutions.jts.geom.Coordinate;
import com.vividsolutions.jts.geom.Geometry;
import com.vividsolutions.jts.geom.GeometryCollection;
import com.vividsolutions.jts.geom.GeometryFactory;
import com.vividsolutions.jts.geom.LineString;
import com.vividsolutions.jts.geom.LinearRing;
import com.vividsolutions.jts.geom.Point;
import com.vividsolutions.jts.geom.Polygon;
import com.vividsolutions.jts.geom.MultiPolygon;
import com.vividsolutions.jts.geom.MultiLineString;
import com.vividsolutions.jts.geom.MultiPoint;
import com.vividsolutions.jts.io.ParseException;
import com.vividsolutions.jts.io.WKTReader;
/**
* Class GeometryDemo.java
* Description Geometry 几何实体的创建，读取操作
* Company mapbar
* author Chenll E-mail: Chenll@mapbar.com
* Version 1.0
* Date 2012-2-17 上午11:08:50
*/
public class GeometryDemo {
private GeometryFactory geometryFactory = JTSFactoryFinder.getGeometryFactory( null );
/**
* create a point
* @return
*/
public Point createPoint(){
Coordinate coord = new Coordinate(109.013388, 32.715519);
Point point = geometryFactory.createPoint( coord );
return point;
}
/**
* create a point by WKT
* @return
* @throws ParseException
*/
public Point createPointByWKT() throws ParseException{
WKTReader reader = new WKTReader( geometryFactory );
Point point = (Point) reader.read("POINT (109.013388 32.715519)");
return point;
}
/**
* create multiPoint by wkt
* @return
*/
public MultiPoint createMulPointByWKT()throws ParseException{
WKTReader reader = new WKTReader( geometryFactory );
MultiPoint mpoint = (MultiPoint) reader.read("MULTIPOINT(109.013388 32.715519,119.32488 31.435678)");
return mpoint;
}
/**
*
* create a line
* @return
*/
public LineString createLine(){
Coordinate[] coords = new Coordinate[] {new Coordinate(2, 2), new Coordinate(2, 2)};
LineString line = geometryFactory.createLineString(coords);
return line;
}
/**
* create a line by WKT
* @return
* @throws ParseException
*/
public LineString createLineByWKT() throws ParseException{
WKTReader reader = new WKTReader( geometryFactory );
LineString line = (LineString) reader.read("LINESTRING(0 0, 2 0)");
return line;
}
/**
* create multiLine
* @return
*/
public MultiLineString createMLine(){
Coordinate[] coords1 = new Coordinate[] {new Coordinate(2, 2), new Coordinate(2, 2)};
LineString line1 = geometryFactory.createLineString(coords1);
Coordinate[] coords2 = new Coordinate[] {new Coordinate(2, 2), new Coordinate(2, 2)};
LineString line2 = geometryFactory.createLineString(coords2);
LineString[] lineStrings = new LineString[2];
lineStrings[0]= line1;
lineStrings[1] = line2;
MultiLineString ms = geometryFactory.createMultiLineString(lineStrings);
return ms;
}
/**
* create multiLine by WKT
* @return
* @throws ParseException
*/
public MultiLineString createMLineByWKT()throws ParseException{
WKTReader reader = new WKTReader( geometryFactory );
MultiLineString line = (MultiLineString) reader.read("MULTILINESTRING((0 0, 2 0),(1 1,2 2))");
return line;
}
/**
* create a polygon(多边形) by WKT
* @return
* @throws ParseException
*/
public Polygon createPolygonByWKT() throws ParseException{
WKTReader reader = new WKTReader( geometryFactory );
Polygon polygon = (Polygon) reader.read("POLYGON((20 10, 30 0, 40 10, 30 20, 20 10))");
return polygon;
}
/**
* create multi polygon by wkt
* @return
* @throws ParseException
*/
public MultiPolygon createMulPolygonByWKT() throws ParseException{
WKTReader reader = new WKTReader( geometryFactory );
MultiPolygon mpolygon = (MultiPolygon) reader.read("MULTIPOLYGON(((40 10, 30 0, 40 10, 30 20, 40 10),(30 10, 30 0, 40 10, 30 20, 30 10)))");
return mpolygon;
}
/**
* create GeometryCollection contain point or multiPoint or line or multiLine or polygon or multiPolygon
* @return
* @throws ParseException
*/
public GeometryCollection createGeoCollect() throws ParseException{
LineString line = createLine();
Polygon poly = createPolygonByWKT();
Geometry g1 = geometryFactory.createGeometry(line);
Geometry g2 = geometryFactory.createGeometry(poly);
Geometry[] garray = new Geometry[]{g1,g2};
GeometryCollection gc = geometryFactory.createGeometryCollection(garray);
return gc;
}
/**
* create a Circle 创建一个圆，圆心(x,y) 半径RADIUS
* @param x
* @param y
* @param RADIUS
* @return
*/
public Polygon createCircle(double x, double y, final double RADIUS){
final int SIDES = 32;//圆上面的点个数
Coordinate coords[] = new Coordinate[SIDES+1];
for( int i = 0; i < SIDES; i++){
double angle = ((double) i / (double) SIDES) * Math.PI * 2.0;
double dx = Math.cos( angle ) * RADIUS;
double dy = Math.sin( angle ) * RADIUS;
coords[i] = new Coordinate( (double) x + dx, (double) y + dy );
}
coords[SIDES] = coords[0];
LinearRing ring = geometryFactory.createLinearRing( coords );
Polygon polygon = geometryFactory.createPolygon( ring, null );
return polygon;
}
/**
* @param args
* @throws ParseException
*/
public static void main(String[] args) throws ParseException {
GeometryDemo gt = new GeometryDemo();
Polygon p = gt.createCircle(0, 1, 2);
//圆上所有的坐标(32个)
Coordinate coords[] = p.getCoordinates();
for(Coordinate coord:coords){
System.out.println(coord.x+","+coord.y);
}
}
}