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From: Paul Hirose (no email)
Date: Tue Jul 20 2004 - 16:14:23 EDT
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.
Recently I heard an LA fire engine respond on an assistance call into
Kern County. They had difficulty locating the assignment, and said
that in the future they would need a Thomas Brothers map reference
from the dispatcher.
Having totally incompatible georeferencing systems in two adjacent
counties is common in the United States. According to a 2002
government report:
"Table 44 and 45 (pp. 89-90) collectively address the ability of fire
departments to access a map coordinate system with sufficient
standardization of format to provide effective functionality in
directing the movements of emergency response partners.
"Table 44 indicates that nearly half of all fire departments have no
map coordinate system. This is a problem particularly for smaller
communities, up to 99,999 population. About one-seventh of all
communities with at least 500,000 population have no map coordinate
system.
"Table 45 indicates that the vast majority of departments with a map
coordinate system have only a local system, which means the system
they have is unlikely to be usable with global positioning systems
(GPS) or familiar to, or easily used by, non-local emergency response
partners, such as Urban Search and Rescue, the National Guard, and
state or national response forces. Moreover, interoperability of
spatial-based information systems, equipment, and procedures will
likely be rendered impossible beyond the local community under these
circumstances. This reliance almost exclusively on local systems
exists across-the-board, in all sizes of communities."
I suspect the use of a coordinate system is more common in the big
counties of the West. It would be hard to function without one, due to
the great areas involved. For example, Kern County is 8070 square
miles, bigger than the state of New Jersey. Two other counties in
California are even bigger.
As far as I can tell from the radio traffic, LA and Kern county fire
and sheriff units navigate the old fashioned way, with paper maps and
pilotage. Dispatchers announce the location's street address and
bracketing cross streets. Sometimes it's an obscure place and
responding units have to discuss the route on the radio, or get talked
in by the dispatcher.
GPS is obviously available on fire engines, because they're able to
provide lat/lon when they need a helicopter to land. In fact, "GPS" is
sometimes synonymous with lat/lon coordinates. A fireman might say on
the radio, "I have GPS for the medevac copter, when you're ready to
copy."
However, the fire and sheriff departments I monitor don't seem to use
electronics for navigation. And any system whereby the dispatcher
could load coordinates directly into a vehicle's GPS receiver is pure
science fiction, at least in my area.
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