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Our rural, mountainous county in Virginia went to what they call "911"
addressing about 4-6 years ago.  There is now a street name and number
for every street and house, and street signs have been installed on all
the roads, including private roads (driveways with more than one
house).  The post office switched to using this new addressing scheme,
which enables most people to learn their "911" address.  The fire
departments, ambulance services and police agencies are provided with
complete, indexed street maps that also show the house numbers by grid.
  "Central dispatch," who receives the calls, provides the address to
the appropriate responder.  (For those not in the U.S., if you have
need of emergency assistance for ambulance, fire or police, dialing 911
on your telephone connects you with "central dispatch").  I believe the
address of land-line phones comes up on "central dispatch's" screen
when they receive a 911 call; cellular phones also are being tied into
this system, I believe, based on the cell they are in; there is talk of
tying a GPS unit in the phones into the system.

I had occasion to use the 911 maps a few years ago, and they were
remarkably accurate.  A few times, street names changed inexplicably or
street numbers did not increment the way one would expect, but that's
to be expected with land maps.  I estimate our 911 maps show about 1
mile per 4 inches, although this is a guess as I can't locate them
currently.

I don't know whether the fire departments also have maps for adjacent
counties.

I believe this was paid for by the Federal Government.  It also
occurred in Kentucky before I moved here; it was aggravating having my
street address changed without moving the house!

Fred

On Jul 20, 2004, at 4:14 PM, Paul Hirose wrote:

> George Huxtable wrote:
>>
>> The trouble with many road atlases is in their gridding. In many
>> cases, the
>> grid markings relate only to each map-page and are unrelated to the
>> gridding of adjacent map-pages and bear no relation to a national
>> coordinate system or to latitude or longitude or WGS84. So there's no
>> way
>> to relate them to coordinates taken from a GPS receiver.
>
> Based on what I've heard on my scanner, the Los Angeles County Fire
> Department "coordinate system" consists of the map page and grid
> square from the Thomas Brothers road atlas! On the other hand, Kern
> County Fire uses the township and section number from the U.S. public
> land survey system. Neither system is usable with common GPS
> receivers.

   

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