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: Jared Sherman
Date: 2004 Jun 19, 23:56 -0400
From: Jared Sherman
Date: 2004 Jun 19, 23:56 -0400
Perhaps something is lost in translation here? Why would it be fortunate that a GPS did not produce an error signal under any condition? GPSes don't produce an error signal per se but they all have means to show a degraded signal, unreliable signal, lack of signal, and similar conditions. They often will show how many satellites are being tracked, along with the signal quality from each, and display a "2D" versus "3D" indicator to show that 3 or 4+ satellites have been acquired. Plus, they often have an "EPE" estimate position error reading which in turn tells you pretty quickly if the GPS has resolved a position well, or not. Yes, GPSes can readily be jammed. There was an incident about two years ago and the comment from the military was "and we can target the jammers" and blow them up very easily. Drop a sextant, and you've got a pile of scrap metal in your hands. Drop a GPS...and it usually has no problem. Both systems have problems. Only one works when there is a 100% overcast and no visible sky. I think the topic has been sufficiently flogged to death in previous years here.
