SQL Server GEOGRAPHY STIntersection 更改点顺序

如何解决SQL Server GEOGRAPHY STIntersection 更改点顺序

是否有可能以与原始对象相同的点顺序获得STIntersection()的结果？

DECLARE @g geography;  
DECLARE @h geography;  

SET @g = geography::STGeomFromText('polyGON((25.84568061650872 49.69890972163677,25.844941083373904 49.69189373653131,25.900405504271674 49.69173426681988,25.900898532630585 49.69667747509544,25.84568061650872 49.69890972163677))',4326);  

SET @h = geography::STGeomFromText('LInesTRING(25.84863871143376 49.68886378946257,25.85578746277756 49.702736200117556,25.874275603076814 49.69013957742882,25.88117784964471 49.696518021079896,25.890791686361744 49.693647826244444)',4326);  

SELECT @g.STIntersection(@h)   

-- output is MULTILInesTRING ((25.890791686361744 49.693647826244444,25.881177849644711 49.696518021079896,25.876080243405344 49.691807467094165),(25.871810347453074 49.691819790540073,25.862392696595393 49.698236908740775),(25.85364996544109 49.698589185269235,25.8501925460631 49.691879772894147)) 

如果你查看输出 here 为例，你会发现它就像颠倒了一样。

我不知道它是否真的颠倒了，它是点和线段的随机顺序，但我需要它们以“原始”顺序保存线方向。

有什么解决办法吗？

谢谢。

解决方法

... 将@h 线串拆分为单条线的有序列表（每条线的起点是线的参考点），将每条单线与多边形@g 相交，并将交点拆分为单独的行（如果不止一个）。如果交点的起点更接近参考点，则保持交点不变，否则将其反转（交点的终点成为起点，反之亦然）。最后按顺序聚合几何集合中的交点（参考点/线序，相交线序）

DECLARE @g geography;  
DECLARE @h geography;  

SET @g = geography::STGeomFromText('POLYGON((25.84568061650872 49.69890972163677,25.844941083373904 49.69189373653131,25.900405504271674 49.69173426681988,25.900898532630585 49.69667747509544,25.84568061650872 49.69890972163677))',4326);  
SET @h = geography::STGeomFromText('LINESTRING(25.84863871143376 49.68886378946257,25.85578746277756 49.702736200117556,25.874275603076814 49.69013957742882,25.88117784964471 49.696518021079896,25.890791686361744 49.693647826244444)',4326);  

--reverse linestring..test
--SET @h = geography::STGeomFromText('LINESTRING(25.890791686361744 49.693647826244444,25.84863871143376 49.68886378946257)',4326);  

select 
concat(
'GEOMETRYCOLLECTION(',string_agg(directionline.ToString(),',') within group (order by pnum,ilnum),')'
) as geometrycollection_string

 --geography::CollectionAggregate(directionline) -- no option for order...
from
(
select 
p.pnum,io.ilnum,case when
--reverse the interection when starting point is farther to the reference point
io.iline.STStartPoint().STDistance(p.spoint) > io.iline.STEndPoint().STDistance(p.spoint)
then 
--...assume intersection is linestring since @h is linestring 
cast(
  replace(
    concat( --lazy...string manipulation
      cast('linestring(' as varchar(4000)),translate(io.iline.STEndPoint().ToString(),'()','  '),translate(io.iline.STStartPoint().ToString(),')'
    ),'point','') 
as geography)
--if the starting point of the intesection is closer to the reference point then keep the intersection as is
--this also covers if intersection is point (when @h is tangent to @g)
else io.iline end  as directionline

from
(

select 
    @h.STPointN(n.pnum) as spoint,--starting point of each line/reference
    n.pnum,--starting point ordinal
    --linestring starting from spoint till the next point
    cast(
      replace(
        concat(
          cast('linestring(' as varchar(4000)),--lazy...
          translate(@h.STPointN(n.pnum).ToString(),translate(@h.STPointN(n.pnum+1).ToString(),')'
        ),'') 
    as geography) as thelines --each line of the @h linestring
from
    (
        --points (excluding the last) of the @h linestring
        select top (@h.STNumPoints()-1) row_number() over(order by @@spid) as pnum --point number
        from (values(1),(1),(1)) as a(n)
        cross join (values(1),(1)) as b(n)
    ) as n

) as p   

--get each intersection "object" of each line (in the @h linestring) with @g
cross apply
(
    --intersection of each line (of the @h linestring) with the polygon @g
    --the intersection could be multiple "objects",get each object
    select p.thelines.STIntersection(@g).STGeometryN(n.ilnum) as iline,ilnum
    from
    (
        --split any multi-object intersection into individual objects
        select top (p.thelines.STIntersection(@g).STNumGeometries()) row_number() over(order by @@spid) as ilnum
        from (values(1),(1)) as b(n)
    ) as n
) as io
) as src
--order by pnum,ilnum