今天将上一次路径绘制的坑(上次绘制的是子路径端点的连线)给填了，本文中我将实现一个输入起点和终点经纬度，输出完整路径(包含子路径端点间的真实弯曲情况，完美贴合真实路径)的函数，能够计算准确的路径长度。

经过一番sql的洗礼我终于能够获取完整的规划路径了：

完整路径，完美贴合

路径端点连线，不完美贴合

并且我们将路径规划做成一个Sql函数，要规划路线的话只需要调用函数即可。

select whz_getPathBeta(106.7267,26.5690,106.8046,26.56904,1000);

废话不多说，上sql。

首先是生成路径的sql，参数填写起点终点经纬度和poi搜索范围。函数中首先将用户的起点终点更新入表中，然后获取路径段的数目，最后获取完整的路径图形。

-- 路网表daolu_simp

-- POI表pointsOfInterest2

CREATE OR REPLACE FUNCTION whz_getPathBeta(x1 float8, y1 float8, x2 float8, y2 float8, roadWithin numeric) RETURNS setof geometry AS

$$

declare poiId1 integer;

declare poiId2 integer;

declare segCount integer;

begin

poiId1=whz_updatePoi(x1,y1,roadWithin);

poiId2=whz_updatePoi(x2,y2,roadWithin);

select count(*) into segCount from pgr_withPoints(

'SELECT gid as id, source, target, cost_len as cost, rcost_len as reverse_cost FROM daolu_simp ORDER BY gid',

'SELECT pid as pid, edge_id, fraction, side from pointsOfInterest2',

-poiId1, -poiId2);

return query SELECT whz_getSegGeom(wp.seq,wp.node::integer,wp.edge::integer, segCount,-poiId1,-poiId2) as the_geom FROM pgr_withPoints(

'SELECT gid as id, source, target, cost_len as cost, rcost_len as reverse_cost FROM daolu_simp ORDER BY gid',

'SELECT pid as pid, edge_id, fraction, side from pointsOfInterest2',

-poiId1, -poiId2) as wp;

end;

$$

LANGUAGE plpgsql;

;

然后是往里面插入POI(起点、终点、途径点)的sql:

-- POI表pointsOfInterest2

-- 指定SRID=4326

-- 指定改点在路段的两侧

CREATE OR REPLACE FUNCTION whz_updatePoi(xo float8, yo float8, roadWithin numeric) RETURNS integer AS

$$

declare idRet numeric;

begin

INSERT INTO pointsOfInterest2(x, y, edge_id, side, fraction, the_geom, newPoint)

(SELECT xo, yo,gid,'b',ST_LineLocatePoint(geom, concat('SRID=4326;POINT(',xo,' ',yo,')')::geometry) as fraction,

st_makePoint(xo,yo),

ST_LineInterpolatePoint(geom, ST_LineLocatePoint(geom, concat('SRID=4326;POINT(',xo,' ',yo,')')::geometry))

FROM daolu_simp

WHERE ST_DWithin(geom, concat('SRID=4326;POINT(',xo,' ',yo,')')::geometry, roadWithin)

order by geom concat('SRID=4326;POINT(',xo,' ',yo,')')::geometry

limit 1)

RETURNING pid into idRet;

return idRet;

end;

$$

LANGUAGE plpgsql;

;

最后是获取每一段子路径的完整路径的sql：

-- POI表pointsofinterest2

-- 路网节点表daolu_simp_vertices_pgr

-- 路网表daolu_simp

-- 本方法试用于起点终点都在poi，且一起点一终点

CREATE OR REPLACE FUNCTION whz_getSegGeom(myseq integer, mynode integer, myedge integer, node_num integer,poiId1 integer,poiId2 integer) RETURNS geometry AS

$$

declare geomRet geometry;

declare startFraction float8;

declare endFraction float8;

declare edgeidForPoi integer;

declare pointTmp geometry;

declare nodeTmp integer;

declare edgeTmp geometry;

begin

IF(mynode<0 AND myseq=1)THEN

SELECT node into nodeTmp FROM pgr_withPoints(

'SELECT gid as id, source, target, cost_len as cost, rcost_len as reverse_cost FROM daolu_simp ORDER BY gid',

'SELECT pid as pid, edge_id, fraction, side from pointsOfInterest2',

poiId1, poiId2) as wp1

where wp1.seq= 2;

select pointsofinterest2.fraction into endFraction

from pointsofinterest2

where pointsofinterest2.pid=-mynode

limit 1;

select pointsofinterest2.edge_id into edgeidForPoi

from pointsofinterest2

where pointsofinterest2.pid=-mynode

limit 1;

select the_geom into pointTmp

from daolu_simp_vertices_pgr

where daolu_simp_vertices_pgr.id= nodeTmp

limit 1;

select geom into edgeTmp

from daolu_simp

where daolu_simp.gid=edgeidForPoi

limit 1;

startFraction=st_linelocatepoint(edgeTmp, pointTmp);

if(startFraction>=endFraction) THEN

geomRet=ST_LineSubstring(edgeTmp, endFraction,startFraction);

ELSE geomRet=ST_LineSubstring(edgeTmp, startFraction,endFraction);

end if;

ELSIF(mynode<0 AND myseq=node_num)THEN

SELECT node into nodeTmp FROM pgr_withPoints(

'SELECT gid as id, source, target, cost_len as cost, rcost_len as reverse_cost FROM daolu_simp ORDER BY gid',

'SELECT pid as pid, edge_id, fraction, side from pointsOfInterest2',

poiId1, poiId2) as wp2

where wp2.seq= myseq-1;

select edge_id into edgeidForPoi

from pointsofinterest2

where pointsofinterest2.pid=-mynode

limit 1;

select fraction into endFraction

from pointsofinterest2

where pointsofinterest2.pid=-mynode

limit 1;

select the_geom into pointTmp

from daolu_simp_vertices_pgr

where daolu_simp_vertices_pgr.id= nodeTmp

limit 1;

select geom into edgeTmp

from daolu_simp

where daolu_simp.gid=edgeidForPoi

limit 1;

startFraction=st_linelocatepoint(edgeTmp, pointTmp);

if(startFraction>=endFraction) THEN

geomRet=ST_LineSubstring(edgeTmp, endFraction,startFraction);

ELSE geomRet=ST_LineSubstring(edgeTmp, startFraction,endFraction);

end if;

ELSIF(mynode>0 AND myseq

select geom into geomRet

from daolu_simp

where daolu_simp.gid=myedge;

END IF;

return geomRet;

end;

$$

LANGUAGE plpgsql;

注意，这个sql里面的表名和相关参数是写死的，实际使用的时候需要根据情况调整。

实际应用

例如可以借此实现Cesium的路径规划。在Web端的业务中，使用AJAX请求后端(例如GeoServer)，后端再使用Mybatis或者Sql视图(Sql视图在GeoServer中配置)，调用数据库中写好的该路径规划函数，函数将返回路径的几何图形，后端再将这些几何图形返回给前端进行渲染。

在倾斜摄影上渲染路径规划结果