pgRouting路径规划

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pgRouting路径规划

         pgRouting扩展了PostgreSQL/PostGIS地理空间数据库，以提供地理空间路由功能。在项目中用到，此处简单记录一下过程。

1、数据准备

        路网数据是关键，在保持道路完整性的同时，道路在相交的路口要打断，路口的各道路起点或终点最好是同一个点。同时做好拓扑检查（ArcMap），防止道路自相交、覆盖或被覆盖等拓扑问题。

2、路网入库

        使用pgAdmin在PostgreSQ新建数据库pgroute，并添加 postgis和pgrouting扩展。使用PostGIS工具将路网数据（road，坐标系为4326）导入pgroute数据库。

3、创建路网拓扑结构

--对road表添加起点(source)和终点(target)字段
alter table road add column source integer;
alter table road add column target integer;--为了提升查询效率，需要对这source和target添加索引
create index road_source_idx on road("source");
create index road_target_idx on road("target");--添加道理权重length和rev_length
alter table road add column length numeric;
alter table road add column rev_length numeric;--创建权重
update road set length=ST_Length(geom,true);
update road set rev_length=length;--创建拓扑结构，即为source和target字段赋值，生成road_vertices_pgr
SELECT pgr_createTopology('road',0.000002,'geom','gid');

4、创建最短路径函数

--DROP FUNCTION public.pgr_fromatob(tbl varchar,startx float,starty float,endx float,endy float);CREATE OR REPLACE FUNCTION "public"."pgr_fromatob"(tbl varchar, startx float8, starty float8, endx float8, endy float8)RETURNS "public"."geometry" AS $BODY$ 
declarev_startLine geometry;--离起点最近的线 v_endLine geometry;--离终点最近的线 v_startTarget integer;--距离起点最近线的终点v_startSource integer;v_endSource integer;--距离终点最近线的起点v_endTarget integer;v_statpoint 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_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_perStart float;--v_statpoint在v_res上的百分比 v_perEnd float;--v_endpoint在v_res上的百分比 v_shPath_se geometry;--开始到结束v_shPath_es geometry;--结束到开始v_shPath geometry;--最终结果tempnode float; 
begin--查询离起点最近的线 execute 'select geom, source, target  from ' ||tbl||' where ST_DWithin(geom,ST_Geomfromtext(''POINT('|| startx ||' ' || starty||')'',4326),15)order by ST_Distance(geom,ST_GeomFromText(''POINT('|| startx ||' '|| starty ||')'',4326))  limit 1'into v_startLine, v_startSource ,v_startTarget; --查询离终点最近的线  execute 'select geom, source, target from ' ||tbl||' where ST_DWithin(geom,ST_Geomfromtext(''point('|| endx || ' ' || endy ||')'',4326),15)order by ST_Distance(geom,ST_GeomFromText(''point('|| endx ||' ' || endy ||')'',4326))  limit 1'into v_endLine, v_endSource,v_endTarget; --如果没找到，返回nullif (v_startLine is null) or (v_endLine is null) then return null; end if ; -- 查询起点和起点最近的先的点select  ST_ClosestPoint(v_startLine, ST_Geomfromtext('point('|| startx ||' ' || starty ||')',4326)) into v_statpoint; raise notice 'v_statpoint %',  v_statpoint;-- 查询终点和终点最近的先的点select  ST_ClosestPoint(v_endLine, ST_GeomFromText('point('|| endx ||' ' || endy ||')',4326)) into v_endpoint; raise notice 'v_endpoint %',  v_endpoint;-- ST_Distance --从开始的起点到结束的起点最短路径 execute 'SELECT st_linemerge(st_union(b.geom)) ' ||'FROM pgr_kdijkstraPath ( ''SELECT gid as id, source::integer, target::integer, length::double precision as cost FROM ' || tbl ||''',' ||v_startSource || ', '||'array['|| v_endSource||'] , false, false ) a, ' || tbl || ' b WHERE a.id3=b.gid   GROUP by id1   ORDER by id1' into v_res ;--从开始的终点到结束的起点最短路径execute 'SELECT st_linemerge(st_union(b.geom)) ' ||'FROM pgr_kdijkstraPath( ''SELECT gid as id, source::integer, target::integer, length::double precision as cost FROM ' || tbl ||''',' ||v_startTarget || ', ' ||'array['|| v_endSource||'] , false, false ) a, ' || tbl || ' b WHERE a.id3=b.gid   GROUP by id1   ORDER by id1' into v_res_b ;--从开始的起点到结束的终点最短路径execute 'SELECT st_linemerge(st_union(b.geom)) ' ||'FROM pgr_kdijkstraPath( ''SELECT gid as id, source::integer, target::integer, length::double precision as cost FROM ' || tbl ||''',' ||v_startSource || ', ' ||'array['|| v_endTarget||'] , false, false ) a, ' || tbl || ' b WHERE a.id3=b.gid   GROUP by id1   ORDER by id1' into v_res_c ;--从开始的终点到结束的终点最短路径execute 'SELECT st_linemerge(st_union(b.geom)) ' ||'FROM pgr_kdijkstraPath( ''SELECT gid as id, source::integer, target::integer, length::double precision as cost FROM ' || tbl ||''',' ||v_startTarget || ', ' ||'array['|| v_endTarget||'], false, false ) a, ' || tbl || ' b WHERE a.id3=b.gid   GROUP by id1  ORDER by id1' into v_res_d ;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;raise notice 'v_res %',  v_res;raise notice 'v_startLine %',  v_startLine;raise notice 'v_endLine %', v_endLine;--如果没找到，返回nullif(v_res is null) then   return null;   end if;--将v_res,v_startLine,v_endLine进行拼接 select  st_linemerge(st_union(array[v_res,v_startLine,v_endLine])) into v_res;select  ST_LineLocatePoint(v_res, v_statpoint) into v_perStart; select  ST_LineLocatePoint(v_res, v_endpoint) into v_perEnd; if(v_perStart > v_perEnd) then tempnode =  v_perStart;v_perStart = v_perEnd;v_perEnd = tempnode;end if;--截取v_res SELECT ST_Line_SubString(v_res,v_perStart, v_perEnd) into v_shPath;return v_shPath; 
end;$BODY$LANGUAGE 'plpgsql' VOLATILE STRICT  COST 100
;ALTER FUNCTION "public"."pgr_fromatob"(tbl varchar, startx float8, starty float8, endx float8, endy float8) OWNER TO "postgres";

5、路网测试

     输入起始经纬度坐标，执行sql语句，获取geojson格式最短路径。

 SELECT ST_AsGeoJSON(pgr_fromAtoB('road',108.253264, 40.075626, 108.254826,40.076253));