Subject: Re: [Ecrit] Proposed requirement: split responsibility

From: Andrew Newton <[email-masked]>
Date: Mon, 23 May 2005 14:40:15 -0400

On May 23, 2005, at 2:08 PM, Brian Rosen wrote:
> It's not exactly easy, but given any street address, we can tell you 
> which
> PSAP gets the call.

This says nothing about the split being based on civil address 
boundaries and does not mean that it is.  Other than country code, this 
sounds like a fairly big assumption.  And it has been pointed out that 
there are even parts of the world where the country code does not 
determine the split.

-andy

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From: "Brian Rosen" <[email-masked]>
Date: Mon, 23 May 2005 15:10:02 -0400

Andrew

We seem to be talking past one another.

If you mean "in the big picture, ignoring 100 years of telephony, how is a
PSAP boundary actually defined?", then, clearly, many boundaries are defined
by natural features such as rivers, and most are defined by political
boundaries, which in turn may have boundaries based on natural features.

If you mean "how is routing defined for emergency calls today", then most of
the time, for the cases where there is more than one PSAP per country, it's
defined in terms of wireline telephony footprints, with historical analomies
tossed in.  Many boundaries are (or maybe more accurately, were) really
central office boundaries.  These were all defined by street addresses; they
didn't use polygons back then, and while they may have started with a map,
they translated to where, on what street/number), the boundary lies.

We have to build databases to make ecrit work.  Unless we are going to
believe we can translate civic to geo or vice versa with sufficient
accuracy, we have to have BOTH civic and geo databases.  Such databases
exist in North America.  I know that there is an effective equivalent in
some other countries, but I don't know enough to even speculate about some
areas.

While in North America, we require a validation step, which implies that we
need a complete database down to house number, we clearly can't get that
immediately everywhere.  Our solution has to deploy incrementally.  If all
calls within a country go one place, we want to have one entry in the geo
and civic routing database for that country.  If there are a couple of large
regions, they are often defined on state/province boundaries, and we can put
entries for every state/province in the civic, and a couple of polygons in
the geo databases, to get started.

If you have a case where most of the countryside goes one place, but one or
more large cities have their own PSAPs, we put the high level entry in, and
also have the lower level entry, and we need the mapping function to look
for the most specific (longest prefix) match.  In North America, boundaries
may be very convoluted (all of a city, plus a couple of streets, minus some
street numbers on one of those streets).

But the bottom line is that routing data today is most often civic address
based.  Geo based routing is available in most places, applied mostly to
mobiles, and may have different routing than wireline.

Brian	
> -----Original Message-----
> From: Andrew Newton [mailto:[email-masked]]
> Sent: Monday, May 23, 2005 2:40 PM
> To: Brian Rosen
> Cc: [email-masked]; 'Ted Hardie'; 'Henning Schulzrinne'
> Subject: Re: [Ecrit] Proposed requirement: split responsibility
> 
>