On Fri, Mar 26, 2010 at 5:01 PM, M.E.Dodd <[email protected]> wrote:
> Is it possible to find the nearest point in one table compared to points in > another table BUT without using the same point in the second table more than > once. > I have one table of points and want to find the nearest point in another > table, the trouble is that some points in the second table are used many > times and others are not used at all even though they are only slightly > further away. There are different numbers of points in each table, each > table has hundreds or thousands of points. The multiple use of points in > the second table like this might be biasing the analysis. > Effectively, an iterative process should work (although I am not sure you can do it with QGIS). Effectively, you have to eliminate the point from dataset two after it is identified as "nearest point" to one in dataset one. But there is one aspect you have to consider: there will be more then one solution, and you have to decide, which one you want to choose - shortest sum of distances possibly? In addition, you will get different solutions, depending on which point in dataset one you begin with. So effectively: yes, it is possible but you have to define your problem more accurately and it requires an iterative approach, with (likely) an optimisation I don't know if it can be done in QGIS. Cheers, Rainer > > > -- > The Open University is incorporated by Royal Charter (RC 000391), an exempt > charity in England & Wales and a charity registered in Scotland (SC 038302). > > _______________________________________________ > Qgis-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/qgis-user > -- NEW GERMAN FAX NUMBER!!! Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation Biology, UCT), Dipl. Phys. (Germany) Centre of Excellence for Invasion Biology Natural Sciences Building Office Suite 2039 Stellenbosch University Main Campus, Merriman Avenue Stellenbosch South Africa Cell: +27 - (0)83 9479 042 Fax: +27 - (0)86 516 2782 Fax: +49 - (0)321 2125 2244 email: [email protected] Skype: RMkrug Google: [email protected]
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