pgRouting：从边缘

Question

我正在尝试找到一种从线串上最近点到我当前位置（lat，long）的路径。到目前为止，我能够获得最短的路径，但它从线串（也称为源）的最开始。我正在使用prg_trsp http://docs.pgrouting.org/2.0/en/src/trsp/doc/index.html 因为它有一个功能来指定沿线串的起始位置。我能够正确计算沿线串的距离并将值传递给函数，但无法弄清楚如何使用函数的结果（pgr_costResult []）来指定路径应该从哪里开始（部分沿着最近的线串）。

当我将路由算法的结果连接到边缘表以获取几何体时，我感觉我在连接时出错了，因为当我加入它时使用边缘表的完整几何体和不是段。虽然，查看文档，但我不知道从路由功能中获取返回段的位置。

以下是我要做的事情（红线）和我所拥有的（蓝线）截图，该点是当前位置。红线来自于使用qgis中的pgrouting插件和trsp（边缘）选择。

见下面的代码：

非常感谢任何帮助！

SELECT st_linemerge(edgeTable.geom_way) FROM pgr_trsp('SELECT id, source, target, cost FROM edgeTable', 
    (SELECT id FROM origin),
    (SELECT * FROM sourcePos),
    (SELECT id FROM destination),
    (SELECT * FROM destPos),
    false, false) AS shortestPath
    JOIN edgeTable ON shortestPath.id2 = edgeTable.id;

origin是起始路线的ID

sourcePos是沿线串偏移

的距离

destination是结束线串的id

destPos是结束线串的分数

此处指定的全部内容：http://docs.pgrouting.org/2.0/en/src/trsp/doc/index.html

Answer 1

这是因为pgr_trsp（）函数没有给出您所例外的输出。 QGIS中的Pg_routing插件对从pgr_trsp（）生成的路由进行捕捉。因此，您将红线的输出贴近了您的点。因此，仅pgr_trsp（）不会为您提供所需的输出。您正在尝试做的事情有些复杂，但可能。这是我解决此问题的方法

    WITH 
    --Make a start point
    start_pt as (
            select st_setsrid(st_makepoint(204845.95, 2410097.47), 32643) as starting),
    --Make a End Point
    end_pt as (
            select st_setsrid(st_makepoint(204937.15, 2409430.86), 32643) as ending),
    --Select Closest source node and its geom for start point
    source_code AS (
            select source, geom from edgeTable order by st_distance(geom, (select starting from start_pt)) limit 1),
    --Select closest target node and its geom for end point
    target_code AS (
            select target, geom  from edgeTable order by st_distance(geom, (select ending from end_pt)) limit 1), 
    --Route Union from pgr_trsp()
    route as (
            SELECT ST_LineMerge(ST_union(geom)) as geom, round( CAST(float8 (st_length(ST_union(geom))/1000) as numeric), 2) as length from (
                SELECT geom FROM pgr_trsp(
                    'SELECT feat_id as id, source, target, cost_len as cost, geom FROM edgeTable',
                    (select source from source_code), (select target from target_code), false, false
                    ) as di JOIN edgeTable
                ON di.id2 = edgeTable.id) as foo)

--Finaly snap the route to precisely matach our start and end point  
select ST_Line_Substring(geom,
                            ST_LineLocatePoint(geom, (select starting from start_pt)),
                            ST_LineLocatePoint(geom, (select ending from end_pt)))
                                from route

我唯一的问题是我必须在最后一个选择语句中切换起点和终点。这可以通过编写函数来处理。这是我的输出

希望此帮助...