News for GPS users

Error due to Selective Avalability used to be about 30 to 40 feet in both the horizontal and vertical axis. I just got back from my patio and my Delorme Earthmate/Laptop combo now says that the error to to SA is now 9 to 10 feet! What an improvement. :)

You realize the Gore will try to claim credit for this. :rolleyes:
 
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Watch-Six:
I can't believe that Clinton finally did something that doesn't piss me off. I must not understand what he is really up to. ;)

[/quote]

Try the Chinese - they probably need the back-up input to ensure those new missiles will, in fact, connect with their targets (us, among others) when launched from that new boomer they got from USSR that they are "modernizing" - maybe from the old Long Beach Naval Shipyard - or even the Canal ... both of which they now control.

Remember ... the neutron bomb concept eliminates people, keeps the real estate intact. They gotta put all those people somewhere ... keeps earth from spinning off into space with that surface weight growing all the time in one place ( :)).

I sincerely hope that we all begin to understand the potential future.

AndyB
United States Navy, (Retired)
 
Dont really see the big deal. Dont have GPS unit, but does the change from 40 feet to 10 really make that big a difference?? Unless you are going to be out walking about in the dark and relying on only the GPS unit to not walk off a ledge. Maybe IFR pilots could use the difference, but I dont see what all the bruha is all about. More than likely DoD was getting fed up having to buy special units to decode the signals and wanted off the shelf prices for their products. Isnt DoD trying to go to off the shelf stuff on as many items as possible? Maybe the Chinese didnt want to have to buy special equipment to guide their troops/missles. Billy "Blow-me" just put a spin on an economic decision to make himself and his party look like the people's representative.
 
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by TAZ:
Dont really see the big deal. Dont have GPS unit, but does the change from 40 feet to 10 really make that big a difference?? ......[/quote]

TAZ, There have been a couple times when running a boat in a narrow ICW channel that I wished I knew within 5 feet where I was.

AndyB
 
SA is to send bad data at a regular interval. This is most noticable when you see your compass on the GPS point in random directions whether your moving or standing still. There are two reasons they are disabling SA. One is for safety because GPS is now used in aviation.

Shok
 
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jcoyoung:
Has anybody ever tried their GPS unit during a commercial jet flight? I have one for my laptop and I decided to try and get some signals by sticking the receiver by the window. It sure took long enough to get 4 sattelites, but I finally got a 3D fix. Kinda strange to see the GPS read the speed at 450+MpH.[/quote]

Jcoyoung, I personally have not tried my GPS unit on an aircraft flight but I believe that there was a recent article in Monitoring Times or Pop Comm where the author of an article covered the legalities concerning utilizing electronic devices (GPS, Ham, Laptop, Scanner) aboard commercial flights.

He also noted that it was extraordinary to watch his GPS display while he was whisking along at 450+mph. I remember that he was also using a laptop and a remote antenna that he placed directly on the window.

My unit has a maximum speed indicator in its trip log mode. The highest speed that I can get it to register is only 125mph. ;)

Skyhawk



[This message has been edited by Skyhawk (edited May 03, 2000).]
 
IIRC, the flight attentant said something like "please turn off cell phones, radios, and 2-way pagers." I believe laptops are ok to use during flight (not during takeoff and landing though). I'm not so sure about GPS receivers though. I'll have to look for that article.

I use the GPS for road trips, so I'm only used to seeing the speed at 70-80Mph. ;)

125Mph :eek: I've approached 115, but that's all. I'll need a car that dosn't feel like it's levitating at speeds over 100. :rolleyes: Time for a vette! :D (or Z28/TA on my budget)

[This message has been edited by jcoyoung (edited May 03, 2000).]
 
So big brother is no longer going to interfere with my GPS unit. Well that is the first thing Klinton has done right in eight years.
 
SA is not turned off, it is turned down. It works like a thermostat, in that it can be turned way down or way up. The results affect what is known as User Range Accuracy (URA). SA is the sum of two components, epsilon (ephemeris fibbing) and dither (clock variations). In affecting epsilon the US government lies just a little bit about the NAVSTAR satellite(s) location(s), thereby degrading signal accuracy; the satellite(s), in a manner of speaking, act as man made stars. Dither are simply clock variations whereby the government lies about the time "frame" on the C/A Code so that your autonomous GPS receiver does not know exactly when the C/A code left the satellite(s). Prior to the reduction of SA on 1 May '00 a Standard Posiotioning Service (the service that's available to non-military) autonomous GPS receiver accuracy was 100 meters 95% of the time horizontally. The vertical accuracy was generally half of the horizontal accuracy at two sigma.

Now that SA is "off" your receiver should achieve accuracys of apporimately 10 to 15 meters horizontally. The variations has to due with the vagaries of the ionosphere and troposphere which the GPS signals pass through prior to reaching the receiver's antenna. For high precision applications (machine control, land survey, precision agriculture) two GPS receivers are still needed to achieve a higher level of accuracy and precision (milimeters to a centimeter or two).

------------------
It is far better to dare mighty things, though riddled with failure, than to live in the dull grey of mediocrity.


[This message has been edited by Mendocino (edited May 08, 2000).]
 
I picked up a Garmin eTrex this weekend (along with some other geek toys). Acquired 4 birds the first time out, accuracy reported at 15 feet. Good enough for me. :)
 
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