Subject: RE: [Geopriv] coordinates

From: "Winterbottom, James" <[email-masked]>
Date: Fri, 18 Nov 2005 09:07:52 -0600

Unless you need better than 30 metres accuracy I would just define a
zone and say that you are in the zone served by the WiFi access point
and not bother about the triangulation at all.

> -----Original Message-----
> From: Brian Rosen [mailto:[email-masked]]
> Sent: Saturday, 19 November 2005 1:50 AM
> To: Winterbottom, James; 'James M. Polk'; 'Henning Schulzrinne'
> Cc: [email-masked]
> Subject: RE: [Geopriv] coordinates
> 
> Possibly a bit of hijacking of a thread, but....
> 
> I've wondered several times how we would actually use a triangulated
WiFi
> location.  Presume there are several WiFi access points and presume we
can
> triangulate between them.  What should we do with that?  I see two
> possibilities:
> 
> 1. Measure, with some difficulty (possibly a lot of difficulty) the
geo
> coordinates of each of the APs with some accuracy.  Triangulate, and
> compute
> the complete geo coordinate of the result.
> 
> 2. Compute the offset from one of the APs and report the location of
the
> AP
> as a civic and the offset as a geo as this thread suggests.
> 
> The attraction of the former is that you get the real coordinates of
the
> device, which, in simplistic terms is exactly what you want.
> 
> The disadvantage is that, without a precise floor plan, what you have
is
> nearly useless.
> 
> The advantage of the latter is that you might actually be able to use
the
> result (I'm 100' NW of Room 235, Floor 2, Building A at 245 Main
Street).
> It wouldn't be the really nice answer, which might be Room 244, Floor
2,
> ...), but it would be useful.
> 
> The availability of a floor plan would tip the answer, but that is a
> pretty
> big problem.  Until we make floor plans readily available, I think the
AP
> Location + offset is likely to be a lot more useful.
> 
> Brian
> 
> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On
Behalf
> Of Winterbottom, James
> Sent: Thursday, November 17, 2005 9:16 AM
> To: James M. Polk; Henning Schulzrinne
> Cc: [email-masked]
> Subject: RE: [Geopriv] coordinates
> 
> Hmmm!
> 
> Actually I see this application as being much more use in the example
> that Ron and Henning gave than in the general pizza case. The reason
for
> this is that distance using these kinds of techniques will more than
> likely be as the crow flies which is useful in a room or open space
kind
> of situation but less useful in a street and block scenario since the
> crow-flies distances is invariable shorter than the street-trip
> distance, sometimes by several times.
> 
> This is not to say that it is not a useful a function, just that it
may
> not be as useful at it first appears to be.
> 
> Cheers
> James
> 
> 
> > -----Original Message-----
> > From: [email-masked] [mailto:[email-masked]] On
> Behalf
> > Of James M. Polk
> > Sent: Thursday, 17 November 2005 8:55 AM
> > To: Henning Schulzrinne
> > Cc: [email-masked]
> > Subject: Re: [Geopriv] coordinates
> >
> > Henning
> >
> > I wasn't sure what Ron meant (it was one of two), so I guessed wrong
> with
> > how to respond. My bad...
> >
> > I see the needs you list below as quite valid, and can come up with
> > several
> > more.  I see this as an instance of the "where's the nearest Pizza
Hut
> to
> > me" question we brought up years ago.
> >
> > What we're talking about here is the delta (in each
> direction/dimension)
> > from a known point in either format. I don't have my version of
> GMLv3.0 or
> > v3.1 in front of me at the moment, but I would be amazed if this
> wasn't
> > accounted for in the 550 page spec (as everything else was  ;-)
> >
> > And if it is in that spec, we ought to use it here. I'm afraid Ted
is
> > going
> > to have a cow with the thought of this fairly advanced usage written
> in an
> > ID somewhere... d`oh!
> >
> > BTW - when I win the Trump Lotto, I'll be calling someone at
Columbia
> > about
> > naming rights...
> >
> > At 04:15 PM 11/16/2005 -0500, Henning Schulzrinne wrote:
> > >James,
> > >
> > >let me try to add a bit of perspective to Ron's note. The issue is
> that
> > >we're dealing with combined geo/civic coordinates. What we'd like
is
> to
> > be
> > >able to say something like:
> > >
> > >"User is 3 m to the left, 5 m ahead of the (defined) corner of the
> Polk
> > >Auditorium, located at 1214 Amsterdam Avenue, NY, NY". (The
> University
> > >will gladly discuss with you how to get your own named
auditorium...)
> > >
> > >There are several applications for that:
> > >
> > >- directing cameras during classes and lectures
> > >- people proximity detection in large indoor venues such as
stadiums
> and
> > >convention centers
> > >- directional microphones
> > >- matching faces and speakers
> > >- directing jets of water to owners of ringing cell phones
> > >etc.
> > >
> > >I don't think the use of standard geo coordinates (long/lat
degrees)
> > would
> > >be rather inconvenient in this case. Can GML express these types of
> > >reference-point relationships?
> > >
> > >Henning
> > >
> > >James M. Polk wrote:
> > >>Ron
> > >>The PIDF-LO already supports coordinates, borrowing from GML. In
> GMLv3.0
> > >>they define an XY or an XYZ as a point. In GMLv3.1, they changed
> "point"
> > >>to "pos" (for position) to get away from the aspect of defining
the
> > >>precision related to a point.  Here is a paragraph at the bottom
of
> page
> > >>5 from the PIDF-LO ID
> >
>
>>http://www.ietf.org/internet-drafts/draft-ietf-geopriv-pidf-lo-03.txt
> > >>that discusses this, including giving a good reference (with
> section)
> > for
> > >>the coordinate examples:
> > >>"
> > >>The Geography Markup Language (GML) is an extraordinarily thorough
> and
> > >>versatile system for modeling all manner of geographic object
types,
> > >>topologies, metadata, coordinate reference systems and units of
> > >>measurement. The simplest package for GML supporting location
> > information
> > >>is the 'feature.xsd' schema. Although 'feature.xsd' can express
> > >>complicated geographical concepts, it requires very little markup
to
> > >>provide basic coordinates points for the most common use cases.
> Various
> > >>format descriptions (including latitude/longitude based location
> > >>information) are supported by Feature (see section 7.4.1.4 of [16]
> for
> > >>examples), which resides here:
> > >>         urn:opengis:specification:gml:schema-xsd:feature:v3.0
> > >>"
> > >>This should give you a hint that this spec does cover XY and XYZ
> > >>coordinates and where to look for the text of this description.
> > >>At 03:35 PM 11/16/2005 -0500, Ron Shacham wrote:
> > >>
> > >>>Hello.
> > >>>
> > >>>We have found it useful in a tracking application at Columbia to
> > support
> > >>>the notion of coordinates within a specific place, and represent
> this
> > in
> > >>>a presence document.  For example, in an auditorium, we wish to
> keep
> > >>>track of a user's (X, Y, Z) coordinates, with respect to a corner
> that
> > >>>is chosen as the point of reference. Although the pidf-lo format
> > borrows
> > >>>an existing format for representing civil location, might it
> > >>>nevertheless be useful to
> > >>>extend the format to include such a coordinate element?
> > >>>
> > >>>Regards,
> > >>>Ron
> > >>>
> > >>>_______________________________________________
> > >>>Geopriv mailing list
> > >>>[email-masked]
> > >>>https://www1.ietf.org/mailman/listinfo/geopriv
> > >>
> > >>cheers,
> > >>James
> > >>                                 *******************
> > >>                 Truth is not to be argued... it is to be
presented.
> >
> >
> > cheers,
> > James
> >
> >                                  *******************
> >                  Truth is not to be argued... it is to be presented.
> >
> > _______________________________________________
> > Geopriv mailing list
> > [email-masked]
> > https://www1.ietf.org/mailman/listinfo/geopriv
> 
>
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