Peter - there is one additional issue here
You imply that if the data is not in WGS84 that the lat and long be
removed ("Those records without a Datum would still be exposed but the
added geo:latitude and geo:longitude fields would be empty.") However -
the lat and long could still be included, but the Uncertainty would be
increased as discussed in the Georferencing Best Practices document
(http://www.gbif.org/prog/digit/data_quality/BioGeomancerGuide) and as
also calculated in the MaNIS Georeferencing calculator
(http://manisnet.org/gc.html)
<http://www.gbif.org/prog/digit/data_quality/BioGeomancerGuide> and in
the BioGeomancer toolkit (http://biogeomancer.org/)
Cheers
Arthur
Peter DeVries wrote:
Arthur Chapman sent me some good comments regarding Datums etc.
The discussion made me realize that there may be a need for two types
of formats. One for the providers and a second one that is output by
the harvesting service.
This is because the needs and abilities of the data providers are
different than the needs and abilities of those who would like to
consume the data.
Consumers, who analyze and map the data, would like something that is
easy to process, standardized and as as error free as as possible.
It could work in the following way.
Data harvesters, like GBIF, collect the records. Run them through
cleaning algorithms that check attributes including that the lat and
long actually match the location described.
These harvesters would then expose this cleaned data via XML and RDF
with tags that flag possible inconsistencies. The harvesters would
also add a field for the lat and long in WGS84 if the original record
contains a valid Datum. Those records without a Datum would still be
exposed but the added geo:latitude and geo:longitude fields would be
empty.
I can imagine that that data uploaded to GBIF and other harvester
services will be replete with typo's and inconsistencies that will
frustrate people trying to analyze or simply map the data, the
harvester services could add value by minimizing these frustrations.
Originally, it seemed that a global service should standardize on a
global Datum like WGS84. After all, we have standardized on
meters? However, after discussing this with Arthur, I realize that
this is not possible for a number of reasons. That said, I think the
data would be much more valuable and less likely to be misinterpreted
if if a version of it was available in WGS84. This solution would
eventually encourage data providers to understand what a Datum is and
include it in their data. It would also help solve a number of other
data integration problems.
Respectfully,
Pete
---------------------------------------------------------------
Pete DeVries
Department of Entomology
University of Wisconsin - Madison
445 Russell Laboratories
1630 Linden Drive
Madison, WI 53706
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