[mapserver-users] distance of a point from a multistring line

[Suman Chatterjee]

Hi,

I am having a table in which I am storing a MULTISTRING after applying
ST_union on a set of multistring data which are continuous. This is
actually the shortest path that I am determining.

Now, I am capturing real time gps coordinates. My plan is that when the
gps position deviates from the determined route it will calculate the
shortest path again from the GPS position.

So I am trying to find the distance of the GPS point from the line (
representing the shortest path) as follows:

 

Select
ST_Distance(gpsdata.gpscoords,ST_line_interpolate_point(shortpath.the_ge
om,ST_line_locate_point(ST_LineMerge(shortpath.the_geom),
GeomFromText('POINT(2477850.34  7044705.10)',2276))) from
gpsdata,shortpath where shortpath.gid=1 and gpsdata.oid=2

 

The coordinates are that of one such gps point.

But I am getting error in the ST_line_locate_point . It says

 

Line_locate_point: 1st arg isn't a line.

 

But when I am running the line_locate_point with some different table
like roads table it works fine.

 

So is there any other way to find the distance of a point to a line?

Thanks

Suman


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