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I have a point data set. Now there are cluster of points based on a field. So I take out one such cluster which has points with same field.I want to find distance between all the points in cluster and find out if any point is far away so that I can check if that point is faulty.

Ok to elaborate more on the above one, I have say just 4 points and I have tried to use the distance matrix from the ftools plugin in QGIS.I have chosen the linear matrix and got a csv output. The distance which gives it here what would be the unit for it.

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2 Answers 2

The distance is probably in degrees. It depends on the projection of the point layer.

You can see a working example of Distance Matrix usage here: Join attribute from nearest point in QGIS

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Thanks , I just figured out it is the ellipsoidal distance in degrees which I have checked in the measure tool. The algorithm is still unclear. And it does not give me any unique id for points. –  Senthil Feb 14 '12 at 9:38
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It's your task to specify the correct unique id columns in the GUI. If your dataset doesn't contain unique ids, you have to add some first. –  underdark Feb 14 '12 at 9:54
    
So I want a distance matrix to be created within a point layer with the input and the output target being the same field which would actually create the matrix . In that case how does the unique ID come out in the output table. The output table just gives the input target , output target and the distance. –  Senthil Feb 14 '12 at 10:16
    
For LatLong, take care that the algorithm calculates the geodesic distances. –  markusN Feb 15 '12 at 0:22

If you want to have the distances between points within one layer using distance matrix you should change k=2, because of this known issue: http://hub.qgis.org/issues/4761

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I had to modify the approach , by using a python script and finding the polygon proximity. –  Senthil Feb 22 '12 at 9:13

protected by whuber Mar 31 at 14:18

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