[geos-devel] Looking for the closest point

[Paul Meems]

Thanks Rémi,

Unfortunately I can't use SpatiaLite or PostGIS.

For now I do this:
1) Break all lines into separate linestrings
2) Search around my location for 1 or more linestrings
3) Create a perpendicular line from my location to the found linestring
4) Use the linestring with the shortest perpendicular line.

I was just wondering if GEOS can already do this.

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
<http://geogis.detek.unideb.hu/TKonferencia/2014/>, in Debrecen Hungary*


2014-03-04 10:50 GMT+01:00 Rémi Cura <remi.cura at gmail.com>:

> Hey,
> if you have access to sql,
> you don't need geos.
>
> You could simply convert line to point then order by distance and get the
> closest.
> Using postgis it would be quiet easy.
> You lines appears to be big, so a simple euclidian distance may give you
> wrong result, you would need a geographical distance.
>
> Cheers,
>
> Rémi-C
>
>
> 2014-03-03 10:35 GMT+01:00 Paul Meems <bontepaarden at gmail.com>:
>
>>  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
>> <http://geogis.detek.unideb.hu/TKonferencia/2014/>, in Debrecen Hungary*
>>
>> _______________________________________________
>> geos-devel mailing list
>> geos-devel at lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/geos-devel
>>
>
>
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