- From: Sean Gillies <sean.gillies@gmail.com>
- Date: Mon, 11 Oct 2010 11:30:56 -0600
- To: Peter DeVries <pete.devries@gmail.com>
- Cc: public-lod@w3.org
Peter, FWIW, there's precedent for point and uncertainty in the "geo URI" RFC: http://tools.ietf.org/html/rfc5870 This would let you express fuzzy locations with fuzzy points instead of precise circles. Cheers, On Mon, Oct 11, 2010 at 10:52 AM, Peter DeVries <pete.devries@gmail.com> wrote: > Hi Paul, > Thanks for bring up these relevant issues. > The geo vocabulary assumes the lat and long are in WGS84. > One of the problems that we were seeing are records that were georeferenced > to the center point of a Canadian Province at it was not clear if that was > actually where the species was observed. Was it at that specific point > or did someone simply tag apply geocode it later to the center of the > province later? Part of this relates to your > comment on provenance. > I had hoped on incorporating both the extent "the actual area that was > sampled" along with the error in the GPS reading to create one all > encompassing radius. Sometimes people will take a GPS reading and then > observe butterflies or plants that are not exactly at that point but within > 50 to 100 meters. > I am hoping that the issues that you mention with New York etc would be in > part of a separate set of statements > using some standard vocabulary like geonames to indicate the county or state > the observation was made. > Thanks Again, > - Pete > > On Mon, Oct 11, 2010 at 9:47 AM, Paul Houle <ontology2@gmail.com> wrote: >> >> On Thu, Oct 7, 2010 at 5:28 PM, Peter DeVries <pete.devries@gmail.com> >> wrote: >>> >>> Hi LOD'ers, >>> There was some discussion about ways to record species observations using >>> the geo vocabulary at a recent biodiversity informatics meeting. >>> Some see the advantages of using the geo standard, but we really need to >>> have a way to incorporate and error or extent in meters. >>> >> >> >> For Ookaboo I've worked out an internal data model for points; >> Ookaboo also knows about real shapes, but the fact is that most people out >> there will throw points at you and only know how to consume points. >> >> Here are a few bits of extra data that are useful to add to a point >> >> (1) provenance >> (2) datum (I try to stick to WGS84, but points from freebase occasionally >> have a Datum attached, so I store it) >> (3) circular error (the accuracy of the determination of the point, for >> instance the technical limitation of a GPS receiver) >> (4) scale length of feature (how accurate do we have to be? it's not >> worth getting into an edit war over the exact point that represents, say, >> Finland.) >> (5) an overall quality rating (so if we've got ten points we can pick the >> best) >> >> Note that (3) and (4) are weakly exclusive of each other. If, for >> instance, I'm representing a GPS point that the camera was at when a photo >> was taken, that's literally just a point, and (4) is zero. On the other >> hand, (4) >> (3) if the point represents "New York City", because you >> can't really fix the location of something that sized to more than a few km. >> >> This distinction is really important in doing data cleaning work. If >> several sources disagree about the location of NYC by a few km, it's best >> to let them "agree to disagree" -- either pick the one you like the best >> (Wikipedia centers NYC at the intersection north of the Port Authority and >> the NY Times building, sweet...) or you take the centroid of them. No >> matter what you do, you want to use a cheap heuristic and not spend >> expensive resources on this non-problem. >> >> On the other hand, if coordinates for the "Statue of Liberty" were >> off by a km from different sources, that indicates that a real problem, >> and some action ought to be taken. >> >> > > > -- > ---------------------------------------------------------------- > Pete DeVries > Department of Entomology > University of Wisconsin - Madison > 445 Russell Laboratories > 1630 Linden Drive > Madison, WI 53706 > TaxonConcept Knowledge Base / GeoSpecies Knowledge Base > About the GeoSpecies Knowledge Base > ------------------------------------------------------------ > -- Sean Gillies Programmer Institute for the Study of the Ancient World New York University
Received on Monday, 11 October 2010 17:31:28 UTC