On Wed, 03 May 2000, Matthew Dillon wrote:
> Ok, this has nothing to do with FreeBSD, but I just had to post
> something since nobody else has.
>
Actually this is pretty relevant to network applications....
Here is some more info from a mailing list I maintain
of tech clippings and other such geek stuff....
This has big implications for network applications
as GPS is now sufficiently accurate to time even
high speed ATM (I believe you need 14ns accuracy
to sychronize to 53 byte cells on an OC3).
cheers,
--dr
---------- Forwarded Message ----------
Subject: kyxspam: GPS descrambled
Date: Wed, 3 May 2000 10:55:47 -0700
From: Dragos Ruiu <[EMAIL PROTECTED]>
(Ok, I'm a network guy, why should I give a flying donut
about GPS descrambling? Well one of the big blocks to
using GPS receivers to synchronizing clocks on sniffers
for high speed networks was the timing uncertainty they
injected to allow military units to be more accurate than
consumer ones. It was possible to use consumer GPS
for high-speed capture synchronization before.... IF you
bought expensive $3-10K differential GPS units that
linked to multiple satellites and made multiple measurements
to remove inaccuracies - making it unfeasible for
distributed systems on cost. The impact of this new
decision means that a whole bunch of new applications
are now possible with consumer stuff with costs in the
hundreds of dollars and not thousands. This now becomes
a perfect method for synchronizing those distributed
gigabit net appliances. Cool... --dr)
url: http://geography.about.com/education/geography/library/weekly/aa050400a.htm
President Turns Off GPS Selective Availability
Dateline: 05/02/00
In plain English, we are unscrambling the GPS signal. It's rare that someone can press
a button and make something you own instantly more valuable, but that's exactly what's
going to happen today. All the people who bought a GPS receiver for a boat or a car,
or their riding lawn mower or whatever, to use in business and in recreation, are
going to find that they're suddenly 10 times more accurate as of midnight tonight. -
Dr. Neal Lane, Director of the Office of Science and Technology.
With SA activated, you really only know if you are on the field or in the stands at
that football stadium; with SA switched off, you know which yard marker you are
standing on. - Comparison of Positions With and Without Selective Availability.
If you take a look at your handheld or automobile Global Positioning System (GPS) unit
today, you'll notice that it's much, much more accurate now than it was on May 1. The
reason? U.S. President Bill Clinton ordered Selective Availability (SA) turned off at
midnight May 1 (Coordinated Universal Time). Now, civilian GPS users around the world
will no longer experience the up to 100 meter (approximate 300 feet) random errors
that SA added to keep GPS a more powerful tool for the military. Today, GPS units are
accurate to within 20 meters (approximately 60 feet); although in good conditions,
units should display an error of less than 10 meters.
In 1998, President Clinton directed that SA should be turned off between 2000 and
2006. Fortunately, it happened early in that range of years. The U.S. military was
able to quickly develop and test their ability to selectively block accurate GPS
transmissions in areas of conflict or where U.S. security was at risk. When the U.S.
Air Force Space Command turned off SA last night, GPS became incredibly accurate for
the entire planet.
GPS operates through the use of 24 satellites, paid for by the U.S. government but
free for the world to use, that are orbiting the earth. The satellites broadcast
extremely accurate time signals (accurate to within 40 billionths of a second) using
their onboard atomic clocks. GPS units on the earth triangulate the time signals from
the satellites to provide location, velocity, and elevation of the units themselves.
When Selective Availability was on, GPS units received a scrambled signal from the
satellites, which hindered private and commercial use of GPS.
The current worldwide GPS industry is estimated to be approximately U.S. $8 billion
and there are about four million GPS users worldwide. Now, experts expect that the
demand and use of GPS will skyrocket, leading to $16 billion industry within three
years. Use of GPS in a variety of areas has automatically been vastly improved. For
example, automobile GPS units and mapping software under SA would often place the car
one to two blocks from its actual location; today, GPS can tell which side of the
freeway a car is on.
GPS is actually now more accurate than the accuracy standard for United States
Geological Survey topographic maps so outdoor enthusiasts should truly appreciate the
new accuracy of their GPS units. Soon, the U.S. Federal Communications Commission will
require location determination technology in cellular phones for use in emergencies as
part of their enhanced 911 service. With a much more accurate GPS system, GPS might be
the technology of choice and emergency responders will be able to respond more quickly
and accurately to these signals from cellular phones.
Future plans for improving the accuracy of GPS include the launching of eighteen
additional satellites that are awaiting launch or are currently in production.
Additionally, two new signals will be broadcast from the satellites by 2005 to help
bypass any distortion from the ionosphere.
For More Information
For general information about GPS, visit my GPS category of links and articles
Statement by the President Regarding the United States' Decision to Stop Degrading GPS
Accuracy
Department of Commerce Fact Sheet on the Civilian Benefits of Discontinuing Selective
Availability
Remarks at White House Press Conference
Comparison of Positions With and Without Selective Availability
The Interagency GPS Executive Board
<LI>For general information about GPS, visit my <a href="/msub48.htm"><B>GPS</b></a>
category of links and articles
<LI><a href="/gi/dynamic/offsite.htm?site=http://www.igeb.gov/sa/potus.txt">Statement
by the President Regarding the United States' Decision to Stop Degrading GPS
Accuracy</a>
<LI><a
href="/gi/dynamic/offsite.htm?site=http://www.igeb.gov/sa/benefits.shtml">Department
of Commerce Fact Sheet on the Civilian Benefits of Discontinuing Selective
Availability</a>
<LI><a
href="/gi/dynamic/offsite.htm?site=http://www.igeb.gov/sa/pressconf.txt">Remarks at
White House Press Conference</a>
<LI><a
href="/gi/dynamic/offsite.htm?site=http://www.igeb.gov/sa/diagram.shtml">Comparison of
Positions With and Without Selective Availability</a>
<LI><a href="/gi/dynamic/offsite.htm?site=http://www.igeb.gov/">The Interagency GPS
Executive Board</a>
--
dursec.com / kyx.net - we're from the future http://www.dursec.com
learn kanga-foo from security experts: CanSecWest - May 10-12 Vancouver
Speakers: Ron Gula/NSW, Ken Williams/E&Y, Marty Roesch/Hiverworld,
Fyodor/insecure.org, RainForestPuppy/wiretrip.net, Theo de Raadt/OpenBSD
Lance Spitzner/Sun, Fyodor Yarochkin/KALUG, Max Vision/whitehats.com
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