Subject: [Geopriv] Making decisions based on location information

From: "Martin Thomson" <[email-masked]>
Date: Wed, 3 Aug 2005 01:54:52 +1000

This is ultimately what ECRIT wants to do, right?  Others might like to do
the same.  There needs to be some sort of guidance on that, so we produced
PIDF-LO profile.

One of the points that Henning made in the GEOPRIV session was that there is
no way of making a recommendation about the minimum precision.  This was
based on the following arguments: that there is no way to ensure that a
100metre uncertainty doesn't cross a boundary, any less than there is to
ensure a 1mm uncertainty doesn't; it was also pointed out that this is
virtually impossible to do with civic location with reference to a number of
interesting cases; finally, that the target would always include all the
information it could if it were available.  He suggested that this be
removed from the draft goals.

After consideration, removing these recommendations from what is intended to
be a BCP might reduce the value of location information.

The first requires a better understanding about the nature of location
information and its determination.  For geodetic in particular, the
determination of a location inevitably leaves some degree of uncertainty.
This leaves a non-zero probability that for any location, that location
could potentially span a routing boundary.  The original aim of this
document is to look at the application space and make a recommendation about
what amount of uncertainty reduces this probability.  If you look at routing
in mobile networks in the US at the moment, cell-size uncertainty is
applied, up to tens of kilometres.  I have heard figures of 30% for calls
being misrouted (that number is from memory, but the order of magnitude is
correct) based on the fact that the uncertainty is so large.  I believe that
a recommendation is beneficial.

Civic location is admittedly a far harder task, and I would concede that any
recommendation has no hope of being comprehensive.  A civic recommendation
can probably be put down as both too hard and impractical.

To address the last, I think that it is worthwhile noting that to achieve a
certain precision requires varying degrees of effort (effort being time,
processing, computing resources, whatever).  Therefore, you might like to
reduce any pre-emptive expenditure of effort before establishing a call.
Now, this doesn't have any impact on emergency calls, which everyone is
focussing on at the moment, but this may impact value-added services - the
local pizza shop case for instance.

Conversely, the target might decide that certain information might not be
pertinent for inclusion in the response, this has already been agreed,
looking at the transforms available in the authorization policy.  For
instance, I might only like to provide very coarse information to someone I
met on the street (I live in Sydney), but that isn't enough to determine
which of the hundreds of pizza stores a call needs to be routed to. In this
case a recommendation provides guidance to whomever specifies the
transformation - that is, don't remove too much information if you want this
to be useful.

M
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From: Henning Schulzrinne <[email-masked]>
Date: Tue, 02 Aug 2005 12:13:45 -0400

> memory, but the order of magnitude is correct) based on the fact that 
> the uncertainty is so large.  I believe that a recommendation is beneficial.

The FCC already makes a "recommendation" (except that that one has real 
teeth, i.e., lawyers, behind it). It's of the 100m order and depends on 
the location technology used (see http://www.fcc.gov/911/enhanced/). If 
we were to recommend a larger value, the FCC and operators would just 
ignore it. If we suggest a smaller value, it is unclear what impact this 
would have. As I said in my remarks, nobody is going to artificially 
lower the resolution for their location-determining equipment for 
emergency calls, so this essentially just guides a technology choice. I 
don't see how we can make such a technology choice with any degree of 
authority. Are we going to say that you have to use WAAS with GPS, even 
though it may not be available in the area you live in?

The additional problem is that there will be some cases where the 
location represents not a user or room, but a whole building or campus. 
If you "require" a resolution below that campus size, you are mandating 
room-level location - something which is not legally mandated in most 
countries. You can guess which recommendation providers will pay 
attention to.

Since the same location information is likely to be used for both call 
routing and dispatch, just worrying about routing is not particularly 
relevant.

> Conversely, the target might decide that certain information might not 
> be pertinent for inclusion in the response, this has already been 
> agreed, looking at the transforms available in the authorization 
> policy.  For instance, I might only like to provide very coarse 
> information to someone I met on the street (I live in Sydney), but that 
> isn't enough to determine which of the hundreds of pizza stores a call 
> needs to be routed to. In this case a recommendation provides guidance 
> to whomever specifies the transformation - that is, don't remove too 
> much information if you want this to be useful.

Beyond the patently obvious "if you want your pizza to reach you, 
country-level information is not likely to be useful (unless you live in 
Monaco or on Antarctica)", what value would a recommendation have?

I don't think padding documents with recommendations that have no sound 
technical basis, depend on technology choices we don't control and are 
likely to be overridden by people who actually matter in this discussion 
serves no purpose except to generate mailing list discussion.

> 
> M
> 
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