Re: GPS

John Sowerby wrote:
> 
>> I'm not sure what you mean by "open system". The GPS system's always 
>> been pretty open, at least the civilian side.
> 
> 
> When first out, the errors in position using civilian GPS could be
quite 
> large, particularly in terms of elevation, all due to the futzing of
the 
> signal by the military. Now, even the standard receivers are much 
> better, as the military have relaxed the rules somewhat.

As I understand it, they simply quit adding the intentional noise. Now 
you're stuck with just natural noise.

> As for usage of GPS, when my father in law to be can plot a course for

> the yacht using his computer, and the thing can steer itself through
the 
> channels in the Port of Miami and down to the Keys, or across to the 
> Bahamas relying on the laptop and the boat's differential GPS system 
> (two receivers and a reference station in South Florida), then the 
> system can no longer be futzed up too badly.

Well, not without warning, at least. They can also add noise only in 
certain areas -- so they could mess up civilian GPS over the Middle East

and leave the Bahamas alone.