Re: [Geopriv] Location measurement error

["Brian Rosen" <br at brianrosen.net>]

Although I am happy to have OGC do the actual work, I think we need to drive
the effort towards a (relatively) swift conclusion.

Towards that end, perhaps we could develop requirements and liaison them to
OGC?

Loc-filters does not touch this issue yet.  My hope is that there is a
result from whatever comes of this discussion which makes an "obvious"
addition to loc-filters to request a notification when a location with a
specified error ("quality") was available.  I certainly want to copy
something else.

Brian

> -----Original Message-----
> From: geopriv-bounces at ietf.org [mailto:geopriv-bounces at ietf.org] On Behalf
> Of Hannes Tschofenig
> Sent: Monday, July 14, 2008 1:26 PM
> To: Carl Reed
> Cc: geopriv at ietf.org; Rosen, Brian
> Subject: Re: [Geopriv] Location measurement error
> 
> I would feel much better if we push these type of things to the OGC (as
> much as we can).
> 
> We have so many other things todo in our group. Additionally, starting
> work on these topics within the IETF smells like a recipe for disaster.
> Finally, we don't have the experts on this subject in the group in order
> to produce a high-quality document.
> 
> I agree with Brian that we should have something in our documents. The
> easiest way for us to get such a work done is to reference something
> that was already discussed and finished in OGC.
> 
> There is only a slight problem with that approach: there are a few
> pieces that reach into our work as well. For example, with the following
> documents there are aspect where uncertainty might reach into our
> protocol work:
> http://www.ietf.org/internet-drafts/draft-ietf-geopriv-policy-17.txt
> http://tools.ietf.org/wg/geopriv/draft-ietf-geopriv-loc-filters/
> 
> I strongly hope that the former document is fine now. I haven't checked
> the loc-filters since it was re-submitted today.
> 
> I would also suggest Martin and Jams to forward their uncertainty
> document to the OGC for review:
> http://tools.ietf.org/id/draft-thomson-geopriv-uncertainty-01.txt
> Maybe Carl has an idea on how to tackle that document.
> 
> Ciao
> Hannes
> 
> 
> Carl Reed wrote:
> > Brian -
> >
> > There is some relevant work done (and being done) in the OGC related
> > to this topic. Let me check on the current status and provide some
> > feedback.  Also, the OGC is totally open to accepting
> > requirements/change requests from the community and using these
> > requirements to help drive enhancements to the OGC standards baseline.
> >
> > FYI, there is an open call for change requests for GML. This open call
> > closes in September. Any individual and/or organization can submit
> > such change requests.
> >
> > So, if the IETF community has any requirements that need to be
> > considered for the next version of GML, please visit
> > http://www.opengeospatial.org/pressroom/pressreleases/879
> >
> > Thanks and regards
> >
> > Carl
> >
> > ----- Original Message ----- From: "Rosen, Brian"
> > <Brian.Rosen at neustar.biz>
> > To: <geopriv at ietf.org>
> > Sent: Monday, July 14, 2008 7:56 AM
> > Subject: [Geopriv] Location measurement error
> >
> >
> >> I'd like to start a discussion on how we deal with, in the big picture,
> >> the notion of measurement error in general and "confidence" and
> >> "uncertainty" in specific.
> >>
> >> I am aware that there are a set of views that go roughly like: "there
> >> really is no such thing as confidence and uncertainty, some vendors are
> >> pushing this idea because they can't do what 'real' GPS devices do and
> >> give you a 3 dimensional error in meters".
> >>
> >> Nevertheless, in one of the most commonly encountered location
> >> determination mechanisms (A-GPS and similar systems), confidence and
> >> uncertainty are reported, and are the only error indicator available.
> >>
> >> In other systems, notably commercial GPS systems, you get a different
> >> kind of error specification.  Sometimes it's simply error in meters,
> >> often with a different value for Z than for x and y.  Other times you
> >> get a more complex representation of error.
> >>
> >> It does seem to me that when we convey measured location, that it would
> >> be appropriate to convey the error of the measurement, and that error
> >> indication should have the ability to represent confidence and
> >> uncertainty.  I think we need to standardize the representation of
> >> error.  It does occur to me to ask if such standardization would better
> >> be done in OGC, and Carl may wish to comment.  It's also possible for
> >> the geopriv crowd to come up with something and then OGC to incorporate
> >> it in a future version of GML.
> >>
> >> If we had a standardized representation of error, then we could also
> use
> >> that in protocols like HELD to request a location within a specified
> >> error bound, and we could also have a filter that requested location
> >> within such a bound.  It would of course, be best to specify the XML
> for
> >> such a bound once.
> >>
> >> I'm specifically proposing that we allow error to be specified one of
> >> two ways initially: with an actual error measurement, in meters for X,
> Y
> >> and Z or as a shape (as in our other shape definitions) with an
> >> "uncertainty" metric in percentage terms.  I would add it to GML if we
> >> could do that, or additional elements in PIDF-LO.  I would then
> describe
> >> an XML data structure to specify a bound, again, either in meters on X,
> >> Y, and Z or confidence as a shape and uncertainty as a percentage.  I'd
> >> allow the representation of both to be extended for other ways to
> >> represent error.
> >>
> >> Brian
> >> _______________________________________________
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> >> Geopriv at ietf.org
> >> https://www.ietf.org/mailman/listinfo/geopriv
> >
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