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I am trying to buffer a point by distances in a table to create a polygon or line for example

For a point with known x,y

buffer based on the following radius: North= 20m East= 21.5m South= 14m West= 26m

Despite trying I haven't been successful does anyone know if this is possible?


Yes am trying to create a circle type shape from the four cardinal points.

enter image description here

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1  
Are these the corners of the polygon, or are you connecting these points using arcs? –  mhoran_psprep Oct 28 '12 at 21:28
    
In case of arcs, it can be done manually in AutoCAD, if you have just a few points. –  nadya Oct 29 '12 at 0:08
    
Sorry I wasnt able to do this QGIS came up with an error as shown? I have tried a few different ways. I should have said I am trying to make a circular shape out of this the method would probably work. Thanks James –  Jampot2000 Oct 30 '12 at 0:37
2  
Can you post a link to an illustration of what you're trying to do? It is rather confusing right now. Are you trying to create a best circle from the four points? –  R.K. Oct 30 '12 at 2:57
1  
Are you trying to do something like this? Dispersion of pollutant? –  nadya Nov 1 '12 at 0:52

1 Answer 1

Not the most elegant solution, but you could use a spreadsheet to calculate WKT (Well-Known Text) descriptions of your vertices, then import them as a geographic shape. For example, in Excel or OpenOffice, create a set of columns with the centre point coordinates (x and y) and the N/S/E/W distances you mention:

Point    x    y    N    S    E    W
Alpha    100  155  20   14   21.5 26

enter image description here

Then, make a column called WKT and use an equation to build the WKT string:

="POLYGON(("&B2&" "&(C2+D2)&", "&(B2+F2)&" "&C2&", "&B2&" "&(C2-E2)&", "&(B2-G2)&" "&C2&", "&B2&" "&(C2+D2)&"))"

Save as a tab-delimited text file, then use the "Delimited text" plugin to import the text file. The plugin should recognise the WKT field, and add the geometry as a layer.

enter image description here

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@user12309, I now see (from the added comment) you're looking for a circular shape, so this won't help. –  Simbamangu Nov 1 '12 at 5:14
    
This is an example of what I am trying to do. dl.dropbox.com/u/36153074/GIS%20query.jpg –  Jampot2000 Nov 14 '12 at 1:41

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