[tdwg-content] data provenance; was Re: Updated TDWG BioBlitz RDF Example with Pivot View and Data Browsing [SEC=UNCLASSIFIED]

[Peter DeVries]

How many times have I said that *standardizing on the number of significance
does not say anything about the the level of uncertainty.*

Again, a rough approximation of the uncertainty is obtained by the *radius*.

Why do you assume that the measure of extent or accuracy follows a normal
distribution?

There is also *no* assumption in *geo* or in the ietf.org proposal that
these are typed as a float. They are a string of characters.

The standardization on the number of significant digits is to standardise
the resulting geo *urn* as a string.

According to the ietf proposal (if it is adopted) is that
"geo:41.53000000,-70.67000000"
and geo:41.53,-70.67" identify the same resource, but they are not the same
urn and
will not be seen as the same urn in a triple/quadstore.

This means that you will not be able to browse between occurrences
associated with the same GPS reading, or search for them via Google.

"geo:41.53000000,-70.67000000" and "geo:41.53000000,-70.67000000" will be
interpreted as the same urn by triplestores, the same string by Google and
the same location by software that correctly interprets the ietf.orgstandard.

Rather than having all the providers rounding to different numbers of
significant digits, standardizing on them makes the resulting data more
comparable.

- Pete


On Tue, Mar 1, 2011 at 7:40 PM, Paul Murray <pmurray at anbg.gov.au> wrote:

>
> On 27/02/2011, at 6:01 AM, Bob Morris wrote:
>
>   "Note: The number of digits of the values in <coordinates> MUST NOT beinterpreted as an indication to the level of uncertainty." The section
> following is also interesting, albeit irrelevant for your procedure. It
> implies that when uncertainty is omitted (and therefore unknown), then "geo:41.53000000,-70.67000000"
>  and "geo:41.53,-70.67"  identify  the same geo resource.
>
>
> This follows from the definition of xs:float, which RDF (and presumably
> geo) borrow. These two strings are each representations of the same IEEE
> floating-point value. Something with a precision is a different datatype.
>
> It seems to me that georeferencing needs a notion of density - some way to
> express a location as a value at a point and a standard deviation (we assume
> a normal distribution). A rectangle becomes an integral of these densities
> at each point - standard deviation of zero corresponding to the usual
> sharply-defined rectangle. You'd probably also want to supply a cutoff
> value.
>
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-- 
---------------------------------------------------------------
Pete DeVries
Department of Entomology
University of Wisconsin - Madison
445 Russell Laboratories
1630 Linden Drive
Madison, WI 53706
TaxonConcept Knowledge Base <http://www.taxonconcept.org/> / GeoSpecies
Knowledge Base <http://lod.geospecies.org/>
About the GeoSpecies Knowledge Base <http://about.geospecies.org/>
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