参考文章:https://blog.csdn.net/wm6752062/article/details/102592487
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 $BODY$
declare
v_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null
if (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)) then
v_res = v_res_b;
end if;
if(ST_Length(v_res) > ST_Length(v_res_c)) then
v_res = v_res_c;
end if;
if(ST_Length(v_res) > ST_Length(v_res_d)) then
v_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null
if(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));