NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: GPS Reliability -- Warnings surely must be a HOAX
From: John Brenneise
Date: 2004 Jun 19, 19:31 -0700
From: John Brenneise
Date: 2004 Jun 19, 19:31 -0700
These warnings are undoubtedly a
HOAX!!!
Read the Bowditch chapter(s) on Electronic
Navigation.
All GPS (Global Positioning System)
satellites transmit on the same two frequencies, modulating a
unique, per-satellite C/A (Course Acquisition) code onto their SPS (Standard
Positioning Service) frequency signal. Civilian GPS
receivers, which use the SPS have internal knowledge of the C/A code
for each satellite from which they are capable of receiving a signal.
SPS receivers employ the C/A code to amplify the signal by
constructive interference, thereby picking out a given satellite's signal from
the "soup".
As you can see, the satellites interfere with each
other BY DESIGN.
The other frequency is used by the PPS (Precise
Positioning Service) which is essentially the domain of military receivers,
but is, nonetheless, also described in Bowditch.
Additional information is available on a variety of
web sites that describe the system.
John Brenneise
----- Original Message -----From: Philip OuvrySent: Saturday, June 19, 2004 2:00 PMSubject: Re: GPS ReliabilityIn the United Kingdom the Royal Institute of Navigation are issuing warnings on the vulnerability of GPS to loss of signal and interference. The received GPS signal is so weak that any interference could stop the GPS receiver completely.With the GPS acting as a back up to normal navigational methods this is not so important. However where navigation is 100% dependent on GPS this could be catastrophic! Fortunately the GPS does not produce an error signal so when it is not working it should be relatively obvious.Philip OuvryPerpignanFrance
