PostGis+GeoServer+OpenLayers最短路径分析

使用PostGis存储路线数据，在GeoServer中发布路网图层和最短路径图层，通过OpenLayers建立路网和展示图层。

1、PostGis：PostgreSQL 12.4,
2、GeoServer：geoserver-2.17.2
3、OpenLayers：6.4.3

一、做成路网数据

1、在PostGis建立路网数据表，主键使用sequence，路网geom 使用geometry(LineString,4326)

CREATE SEQUENCE public.my_roads_id_seqINCREMENT 1START 1MINVALUE 1MAXVALUE 2147483647CACHE 1;ALTER SEQUENCE public.my_roads_id_seq OWNER TO postgres;CREATE TABLE public.my_roads
(id integer NOT NULL DEFAULT nextval('my_roads_id_seq'::regclass),name character varying(32) COLLATE pg_catalog."default",geom geometry(LineString,4326),CONSTRAINT my_roads_pkey PRIMARY KEY (id)
)TABLESPACE pg_default;ALTER TABLE public.my_roads OWNER to postgres;

2、在GeoServer中发布路网图层

建立工作区，建立postgis的数据存储，发布my_roads图层。

EPSG使用4326，边框及经纬度为：【-180，-90 】【180，90】即可。

3、OpenLayers中建立路网

使用vue开发路网编辑画面。

实现方式，请参考：OpenLayers 在Vue中增删改

注意点：新增的线不再是newFeature.setGeometry(new MultiLineString([geometry.getCoordinates()]))

// 转换坐标let geometry = this.drewFeature.getGeometry().clone();geometry.applyTransform(function (flatCoordinates, flatCoordinates2, stride) {for (let j = 0; j < flatCoordinates.length; j += stride) {let y = flatCoordinates[j];let x = flatCoordinates[j + 1];flatCoordinates[j] = x;flatCoordinates[j + 1] = y;}});// 设置feature对应的属性，这些属性是根据数据源的字段来设置的let newFeature = new Feature();newFeature.setId('nyc_roads.new.' + this.newId);newFeature.setGeometryName('the_geom');newFeature.set('the_geom', null);newFeature.set('name', newFeature.getId());newFeature.setGeometry(new MultiLineString([geometry.getCoordinates()]));

而是newFeature.setGeometry(geometry);

// 转换坐标
let geometry = this.drewFeature.getGeometry().clone();
geometry.applyTransform(function (flatCoordinates, flatCoordinates2, stride) {for (let j = 0; j < flatCoordinates.length; j += stride) {let y = flatCoordinates[j];let x = flatCoordinates[j + 1];flatCoordinates[j] = x;flatCoordinates[j + 1] = y;}
});// 设置feature对应的属性，这些属性是根据数据源的字段来设置的
let newFeature = new Feature();
newFeature.setId('am_roads.new.' + this.newId);
newFeature.setGeometryName('geom');
newFeature.set('geom', null);
newFeature.set('name', newFeature.getId());
newFeature.setGeometry(geometry);

编辑好的路网如下：

二、路径分析基础数据

1、路网拓扑生成

-- 创建拓扑布局，即为source和target字段赋值
select pgr_createTopology('my_roads',0.001, 'geom', 'id');--为cost 赋值
update my_roads set cost =st_length(geom);
--为双向reverse_cost 赋值
UPDATE my_roads SET reverse_cost = st_length(geom);--为线的起点和终点坐标赋值
UPDATE my_roads SET x1 =ST_x(ST_PointN(geom, 1));
UPDATE my_roads SET y1 =ST_y(ST_PointN(geom, 1));
UPDATE my_roads SET x2 =ST_x(ST_PointN(geom, ST_NumPoints(geom)));
UPDATE my_roads SET y2 =ST_y(ST_PointN(geom, ST_NumPoints(geom)));

2、最短路径函数

此函数参考网上路径分析函数，解决了计算不准确问题和MultiLineString问题。

建立根据拓扑后节点，计算最短路径函数pgr_shortestpath_edge。

CREATE  OR REPLACE FUNCTION pgr_shortestpath_edge (tbl CHARACTER VARYING,fromNode INTEGER,toNode INTEGER,startLine geometry,endLine geometry)
RETURNS geometry
AS $BODY$
DECLAREv_res geometry;--最短路径分析结果v_linemerge geometry;--合并线后结果v_shPath geometry;--最终结果
BEGIN--从开始的节点到结束的节点最短路径EXECUTE'SELECT st_linemerge(st_union(b.geom)) ' || 'FROM pgr_dijkstra( ''SELECT id, source, target, cost FROM ' || tbl || ''',' || fromNode || ', ' || toNode || ', false ) aLEFT JOIN  ' || tbl || ' b  ON a.edge = b.id ' INTO v_res;-- 合并线select  st_linemerge(ST_Union(array[startLine, v_res, endLine])) into v_linemerge; RETURN v_linemerge;
END; $BODY$ LANGUAGE plpgsql VOLATILE STRICT COST 100;
ALTER FUNCTION pgr_shortestpath_edge ( CHARACTER VARYING, INTEGER, INTEGER, geometry, geometry ) OWNER TO postgres;

建立最短路径函数

CREATE  OR REPLACE FUNCTION pgr_shortestpath ( tbl CHARACTER VARYING, startx DOUBLE PRECISION, starty DOUBLE PRECISION, endx DOUBLE PRECISION, endy DOUBLE PRECISION ) RETURNS geometry
AS $BODY$ DECLAREv_startLine geometry;--离起点最近的线v_endLine geometry;--离终点最近的线v_startPoint geometry;--在v_startLine上距离起点最近的点v_endPoint geometry;--在v_endLine上距离终点最近的点v_startLine_pre geometry; --起点到v_startPoint的线  v_endLine_next geometry; --终点到v_endPoint的线  v_startPoint_pre geometry;  --起点v_endPoint_pre geometry;  --终点v_startTarget INTEGER;--距离起点最近线的目标节点v_startSource INTEGER;--距离起点最近线的源节点v_endSource INTEGER;--距离终点最近线的源节点v_endTarget INTEGER;--距离起点最近线的目标节点v_start_x1 double precision;v_start_y1 double precision;v_start_x2 double precision;v_start_y2 double precision;v_end_x1 double precision;v_end_y1 double precision;v_end_x2 double precision;v_end_y2 double precision;v_startLine_Source geometry;v_startLine_Target geometry;v_endLine_Source geometry;v_endLine_Target geometry;v_res geometry;--最短路径分析结果v_res_a geometry;v_res_b geometry;v_res_c geometry;v_res_d geometry;v_shPath geometry;--最终结果BEGIN--查询离0.01度(大约1000米)范围内起点的最近线EXECUTE'select geom, source, target,x1,y1,x2,y2  from ' || tbl || ' where ST_DWithin(geom,ST_Geometryfromtext(''point(' || startx || ' ' || starty || ')'',4326),0.01)order by ST_Distance(geom,ST_GeometryFromText(''point(' || startx || ' ' || starty || ')'',4326))  limit 1'INTO v_startLine,v_startSource,v_startTarget,v_start_x1,v_start_y1,v_start_x2,v_start_y2;--查询离终点0.01度(大约1000米)范围内的最近线EXECUTE'select geom, source, target,x1,y1,x2,y2 from ' || tbl || ' where ST_DWithin(geom,ST_Geometryfromtext(''point(' || endx || ' ' || endy || ')'',4326),0.01)order by ST_Distance(geom,ST_GeometryFromText(''point(' || endx || ' ' || endy || ')'',4326))  limit 1' INTO v_endLine,v_endSource,v_endTarget,v_end_x1,v_end_y1,v_end_x2,v_end_y2;--如果没找到最近的线，就返回nullIF ( v_startLine IS NULL )  OR ( v_endLine IS NULL ) THENRETURN NULL;END IF;--创建查询的起点和终点  SELECT ST_SetSRID( ST_MakePoint(startx , starty),4326 )INTO v_startPoint_pre;  SELECT ST_SetSRID( ST_MakePoint(endx , endy),4326 )INTO v_endPoint_pre;  --查询线上最接近某点的点（此点在线上）SELECT ST_ClosestPoint ( v_startLine, v_startPoint_pre) INTO v_startPoint;SELECT ST_ClosestPoint ( v_endLine, v_endPoint_pre) INTO v_endPoint;--根据最近点，把最近线分为source和target两段SELECT ST_MakeLine( v_startPoint,ST_SetSRID( ST_MakePoint(v_start_x1 , v_start_y1),4326 )) INTO v_startLine_Source;SELECT ST_MakeLine( v_startPoint,ST_SetSRID( ST_MakePoint(v_start_x2 , v_start_y2),4326 )) INTO v_startLine_Target;SELECT ST_MakeLine( v_endPoint,ST_SetSRID( ST_MakePoint(v_end_x1 , v_end_y1),4326 )) INTO v_endLine_Source;SELECT ST_MakeLine( v_endPoint,ST_SetSRID( ST_MakePoint(v_end_x2 , v_end_y2),4326 )) INTO v_endLine_Target;--计算最短路径（开始的起点/终点 --- 结束的起点/终点）SELECT pgr_shortestpath_edge (tbl, v_startSource, v_endSource, v_startLine_Source, v_endLine_Source) INTO v_res_a;SELECT pgr_shortestpath_edge (tbl, v_startTarget, v_endSource, v_startLine_Target, v_endLine_Source) INTO v_res_b;SELECT pgr_shortestpath_edge (tbl, v_startSource, v_endTarget, v_startLine_Source, v_endLine_Target) INTO v_res_c;SELECT pgr_shortestpath_edge (tbl, v_startTarget, v_endTarget, v_startLine_Target, v_endLine_Target) INTO v_res_d;v_res = v_res_a;IF( ST_Length ( v_res ) > ST_Length ( v_res_b )) THENv_res = v_res_b;END IF;IF(ST_Length ( v_res ) > ST_Length ( v_res_c )) THENv_res = v_res_c;END IF;IF(ST_Length ( v_res ) > ST_Length ( v_res_d )) THENv_res = v_res_d;END IF;--创建查询起点和终点到最近的线之间的线SELECT ST_MakeLine( v_startPoint,v_startPoint_pre) INTO v_startLine_pre;  SELECT ST_MakeLine( v_endPoint,v_endPoint_pre) INTO v_endLine_next;  select st_union(array[v_endLine_next, v_res, v_startLine_pre]) into v_shPath; return v_shPath;
END; $BODY$ LANGUAGE plpgsql VOLATILE STRICT COST 100;
ALTER FUNCTION pgr_shortestpath ( CHARACTER VARYING, DOUBLE PRECISION, DOUBLE PRECISION, DOUBLE PRECISION, DOUBLE PRECISION ) OWNER TO postgres;

三、显示最短路径

1、GeoServer建立创建sql视图

D的默认值全部为0，
验证的正则表达式全部为^-?[\d.]+$
类型选为 Geometry类型，SRD为4326

2、OpenLayer中传参并加载最短路径图层

VUE中增加加载最短路径图层方法：

querypath(){let startCoord = [116.43442149206543,39.927703206481944]let destCoord = [116.410648020996,39.9069321798706]let params = {LAYERS: 'postgis:shortestpath',FORMAT: 'image/png',};let viewparams = ['x1:' + startCoord[0], 'y1:' + startCoord[1],'x2:' + destCoord[0], 'y2:' + destCoord[1]];params.viewparams = viewparams .join(';');let imageLayer = new ImageLayer({source: new ImageWMS({url: 'http://localhost:8088/geoserver/postgis/wms',params: params}),});this.map.addLayer(imageLayer);
},

3、最终结果显示