[geos-devel] Looking for the closest point

[Mike Toews]

Have you tried using NearestPoints(g1, g2)?
http://geos.refractions.net/ro/doxygen_docs/html/classgeos_1_1operation_1_1distance_1_1DistanceOp.html#a6
(and for C-API it is called GEOSNearestPoints).

It will return the closest points along on the linestring from another
geometry (like a point). Normally you might expect one point that is
closest, however it is conceivable there could be many equidistant
closest points to another. Another detail is that the returned
coordinate(s) may not be vertices of the original linestring. If you
need the closest vertex(es), then you should convert the stream to a
multipoint before using NearestPoints.

-Mike

On 3 March 2014 22:35, Paul Meems <bontepaarden at gmail.com> wrote:
>
> Hi List,
>
> We use with MapWinGIS (C++ ActiveX control) GDAL with GEOS.
>
> I've got a linestring (stream) and need to know the closest point at that stream from a specific location.
> What I need is the index of the point in the stream and the distance from the location to that point.
>
> We currently have a custom GetClosestPoint method which is not using GEOS, but that is not working when a long linestring is close to the location but the points are far away.
> For example my line has two points, starts in Amsterdam and ends in Paris. My location is near Antwerp.
>
> Does GEOS have a better method for this? I did searched using Google and found several methods/pages but I'm not sure what to use.
> I also want to make it a generic method that will work with all types of lines and polygons.
>
> Any advice would be much appreciated.
>
> Thanks,
>
> Paul
>
> Paul Meems
> Release manager, configuration manager
> and forum moderator of MapWindow GIS.
> www.mapwindow.org
>
> Owner of MapWindow.nl - Support for
> Dutch speaking users.
> www.mapwindow.nl
>
>
> Join us at the MapWindow GIS Conference 2014, in Debrecen Hungary
>
>
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