[Taxacom] Data quality of aggregated datasets

Robert Mesibov mesibov at southcom.com.au
Tue May 7 06:43:18 CDT 2013


Quentin Groom wrote:

"Why shouldn't taxonomists collect gridded data in the first place, just as ecologist have been for years?"

Many taxonomists used to do so (including me) and probably many still do, if they record locations as UTM grid squares from maps. You read or estimate from the map the easting to the left and the northing to the bottom of the site location. The grid reference thus created is a square within which the site was located. It's then a computational piece of cake to aggregate sets of these squares into larger and larger units, like 1 km squares, 2 km squares, etc., for grid-based analysis. But when I bought a GPS, I no longer needed a map, so I gave up UTM entirely. Lat/lon data are the universal currency for reporting spatial data, and I could get those directly without a UTM-to-geographic conversion.

I'm afraid I don't see your point about gridded data. Point data are fine for recording and mapping localities. They're also OK for biogeographic analysis; see my 2011 parapatry paper in ZooKeys: http://www.pensoft.net/journals/zookeys/article/1893/a-remarkable-case-of-mosaic-parapatry-in-millipedes  In non-taxonomic GIS work in the past I've had no trouble stacking point and grid data and doing analyses based on the two sorts of data. There may be ecological analyses that require gridded data only, but why do you think specimen localities should first be in that form? Aren't ecological analyses generally done at a grid scale much coarser than would be used for recording localities+'errors' as grid squares?
-- 
Dr Robert Mesibov
Honorary Research Associate
Queen Victoria Museum and Art Gallery, and
School of Agricultural Science, University of Tasmania
Home contact: PO Box 101, Penguin, Tasmania, Australia 7316
Ph: (03) 64371195; 61 3 64371195




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