"D" GPS

[amberjack 278]

I'm still using the Ol school loran & plan on getting a gps&differental this spring. The question I'm inquiring is If the goverment throws a curve to GPS units that can be cured w/ a diff. for more precise accuracy.My ? is if they dont want civilians to have precise accuracy why do they let Differentials stay on the market. Are these Legal to purchase & run?

[Bawugna]

Amberjack,

Differential is not the "latest" technology. I do not even know of a company still advertising a differential reciever. Just buy a GPS with WASS. I went from a Differential to WASS and did not really see much of a difference. My new unit, a Garmin 182C, has built in WASS and I already had a Garmin GBR21 Differential installed in the boat. I am able to toggle between Differential and WASS, the 182C cannot use them simultaneously, you have to change your settings a bit.

Don't throw away your Loran though. Keep it and run it too. Loran is not all that outdated and I have heard that the repeatability of Loran beats GPS.....but who knows.

[Phil L]

Supposedly,
The differential beacon give you 1M accuracy as opposed to 15M from a straight GPS. Furuno still makes a differential external beacon and still offers the GP 37 which has an internal beacon.

The newer technology is is WAAS (Wide Area Augmentation System)....with this activated and in an area where it is operational its supposed to give you 3M accuracy.

So with standard GPS your looking at accuracy to 45 ft, 9 ft with WAAS enabled and 3ft with differential GPS supposedly...

Phil L

[TWIN D'S]

jack,

What they're afraid of is someone using our GPS system to send a GPS guided bomb into the living room of the White House. In the event there's a threat of war, the GPS signal can be degraded to limit it's accuracy.

Phil

[aimless2]

I have a Furuno 1850WDF. It has differential and waas. It is set to use the best signal and it always uses differential.

[Capt. Scott]

Most of the big companies still make DGPS recievers because I believe the USCG still has not authorized WAAS for all commercial shipping (IMO - International Maritime Org hasn't either).

WAAS and DGPS are FAR more accurate than Loran even in the repeatability issue. LORAN was a bit better than regular GPS on a bad day. However LORAN is alive, well, and being upgraded by the USCG...hold on to yours if it works.

The only good thing the Clinton's did was to tell the Air Force to stop jamming GPS so regular GPS is even pretty good now for all but finding wrecks or threading the needle while navigating.

I asked the same question back in the late 80's when the FAA was proposing WAAS when the USCG was working on DGPS and the Air Force was spending the same millions to jam it....hell it's legal...it just took the government awhile to figure that even WAAS isn't good enough for ballistic missiles...now cruise missiles are another story!!!!!!!

[ 01-16-2004, 01:08 PM: Message edited by: Capt. Scott ]

[amberjack 278]

Thanks for all your helpful information guys.

[To-Do]

Differential will make it's corrections via land based antennas similar to loran while the wass will use satelites. DGPS and Wass are about the same in accuracy(wass a bit better) assuming that weather conditions do not obstruct the differential signal. Go with the WASS and as said before leave loran and as you re-find your spots w/ loran set the new waypoint into the gps.

[High Wire]

I have an older GPS (1999) with the external Differential receiver. The amount of error with it on or off is still less than a boat length. Unless you plan to navigate 10 ft wide irrigation ditches in fog, you don't NEED Diff or WAAS. Since the govt stopped degrading the GPS, a plain 12 channel is good for 99 percent of the recreational boaters out there. For example, the plot on my Garmin 215 when zoomed down, I can repeat my path in and out of the marina past the BreeZee Lee old gas dock. Thats maybe 50 ft wide. It always shows my boat in its slip. If I leave it on all day in the slip, the little spirograph path in the slip remains within the size of the "boat" position symbol arrow in my slip. Go for a chart plotter GPS. Once you load your loran spots in the plotter, and get used to the operation of the GPS, you won't use the loran again.

[ 01-18-2004, 07:25 AM: Message edited by: High Wire ]

[windmeup]

Highwire said it best! no need to repeat.

[nocturnal]

All questions were answered but,buy a color unit!
Spend the money or you will regret it.

[one eye willy]

Buy a waas you will save $$ you won't need the extra antena! ;)

[Capt Buck]

We've had all three versions of GPS, the select avaiablity one with which you were lucky to be within 30-40 meters in any direction of the original waypoint, DGPS which tightened up the repeatabilty factor quite a bit, and now have a unit with builtin WAAS, the most accurate to date. I've never had any trouble with WAAS other tahn the units seems to loose the WAAS signal every once and a while, but then picks it right back up again. My chioce would be a colour plotter, WAAS GPS.

[CastawayRay]

hmmmmmmm

lets see, an ICBM can carry multiple warheads capable of cratering SOLID ROCK to 1500 feet, ummmmmm, I dont think a couple of meters is going to make a difference!

and as far as finding wrecks and the like, I check the depth finder to see bottom structure, yeah it would be nice to have a buzzer sound off when you are exactly where to be, or better yet, calculate the wind speed, current speed, water depth and amount of rode to put out, and when the boat settles into the hook, BOOM yer on the money

sheesh!

[Ron Redington]

Moving this topic to the Tackle Box, our "General Conversation" forum smile.gif