[Taxacom] Google Maps again

Bob Mesibov mesibov at southcom.com.au
Thu May 6 00:38:44 CDT 2010

Hi, Kip.

It depends how you want to do it. You can either have points plotted as error circles, or points and their error circles as separate KML files.

The second is easier to do but less satisfying. Geo Utilities has an online tool for producing buffers around points; it's well-described at http://freegeographytools.com/2007/online-google-earth-utilities-for-buffering-and-area-calculations Note that the new KML file for the buffer circles has a fixed 'radius' (it's actually a bunch of points on the diameter). If you have a range of errors in your locality data set, that set has to be broken into its different error values. It should be possible to combine the KML files into a single 'MultiGeometry' file but I haven't tried it.

The first would be handy. You'd have a spreadsheet with separate fields for lat, long and error. You'd feed this to a KML generator, and it would produce placemarked circles with radius based on the value in the error field. I say 'would be handy' because I haven't seen this yet. Anyone?

There are of course GIS tools for doing this off the Web, e.g. http://www.spatialecology.com/htools/buffer.php For my own, humble GIS needs I run the venerable ArcView 3.2 (through Wine under Linux, works great). In AV3.2 I can show different size circles for different error values simply by displaying according to 'Unique Value' in the error field (e.g. 25, 50, 100, etc metres) in my attribute table, then adjusting the symbol size and colour to my liking.

Dr Robert Mesibov
Honorary Research Associate
Queen Victoria Museum and Art Gallery, and
School of Zoology, University of Tasmania
Home contact: PO Box 101, Penguin, Tasmania, Australia 7316
03 64371195; 61 3 64371195
Webpage: http://www.qvmag.tas.gov.au/mesibov.html

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