Best nuvi accuracy in feet?

I've been down to 12-13 feet with a Nuvi 660

I've seen it down to 12' or so on my nuvi350.

Best I have had was 13 ft...

In my home office, in front of the computer...and 10 feet out and about in the car.

Looked at it more closely today. Touch at 13 but stabilized at 18 with 10 satellites lock-on. Weather was cloudy and rainy.

10'

Mine is usually set in metres, and I see it fluctuate between 4 m and 6 m ( about 13 to 20 ft) all the time, but the best I have seen in standard is 10 ft. The strange thing is that I have it set with the PIN number and that is supposed to be set up to remember a geographic location as well as the number.
Well, it doesn't unlock until I begin to rive down the street to the corner, where it magically begins to work. Now I set it up in the driveway, so I kind of think it's accuracy level is someplace between my home and the corner, which is about 100 ft. However, it can tell if I'm in the express or collector lanes on the highway!

Best I've seen so far is 12-14 feet pretty regularly with my nuvi 660.

Sounds like 12-14 is pretty standard then, with occasional 10'-accuracy claimed. Is that the industry best at present for non-military GPS?

I also wonder how accurate these figures the nuvi shows actually ARE. It could claim to be within 3 inches and I'm not sure I'd know any better.

I was driving around today and it consistantly stayed at 9 feet, usually around 12 to 15 feet. Heck I've got 26 feet in my BASEMENT right now!

...and manufacturers needless to say want to win your interest or beat the competition by jiggering the numbers to make their gadget look the greatest.

GPS receivers tend to use something called 'estimated position error' which is based only on satellite geometry and doesn't take into account other factors that can cause error. (e.g. as much as the sun looks distorted as it sets or rises because of atmospheric distortion, GPS signals can get bent also as they pass thru the atmosphere at weird angles. Moisture in the air, solar activity, tree cover, etc. also can take a toll. There's also multi-path error, which older cars noticeably had with radio reception such as in cities with skyscrapers and the signals would bounce all over the place before getting to the car's antenna. GPS' can have that too.)

Another method figures out the accuracy that a receiver will have 50% of the time. Another does it at 68% of the time. Another method determines the accuracy it'll have 95% of the time. The 50% figure looks a whole lot better, but it's a lot less meaningful. The 95% figure is far better to use, but it involves a much larger number and so is less impressive. (For those with a statistical background it involves how many standard deviations of error are being employed.)

There's also an interesting reality of accuracy being measured to a particular spot, vs. trying to come back to that spot at a later point. i.e. If the GPS puts you at your home, and say it's actually 25' too far north, it nominally has 25' accuracy. Later, when you return home again it puts you 25' too far south. Still 25' accuracy, nominally, but now it's 50' off.

My 2 cents: my nuvi repeatedly has the curious phenomena of approaching intersections, hiway junctions, and what not and shows me 400' away when I'm only about 100-200' out. And it suddenly makes a massive jump downward in the distance to turn figure. It also is thoroughly confused by parking lots, gas station driveways, etc. that parallel roads but which are not in its internal map. So my guess is that functional accuracy is measured at 100-300 feet. Who really cares: it gets me where I want to go!

GC

12 ft on my Nuvi 660

The best I've seen consistently is 9 feet. I'm not sure if this is a 9 foot radius or 9 foot diameter. I have a nuvi 350 and eTrex Legend and both display about the same accuracy. As another post mentioned, the accuracy displayed could be 50% point or some other criteria. Does anyone know how these Garmin units measure it? I have found that looking for geocache I am generally within +/- 3 feet of the cache and if I look at the display change in the least significant digit it is about 10 feet. I have noticed that the elevation seems a lot less accurate and changes from one day to the next for the same position.

I have the Nuvi 680 and about 14' is the best I have seen however I did notice yesterday on a road trip I switched over to 2D on the map and noiced more accurate positions as I approached intersections opposed to using the 3D map.

GC, Have you tried the 2D map versus the 3D? As I said in my earlier post I see a significant difference when approaching an interection. In 3D it states 200' to 300' but in 2D it is more like 20'. I would assume it is to do with the units ability of mapping in 3D takes more time to display. I have the Nuvi 680 which is very similar to your 660.

The best I've seen was 20 feet... dunno how u guys get so much better

I've never been able to tell the difference and don't have a clue what the 3D does, so I've always used 2D. I still stand behind what I already said, which is that what the units are advertising as accuracy has more to do with hype than reality.

GC

i think it's around 20...

but lately ive noticed choppier screen updates, i think ill try the sd idea

Thanks for the information GC. Very informative.

For civilian purposes, GPS is "fuzzed" down to about 10' accuracy. For the military guys, it's much better, probably down to a few inches. For us, it's a matter of putting a vehicle on the proper ramp. For them, it's missing a mountain top or putting a missile down a stairway.
The funny thing about the Nuvi is that the vertical accuracy can be way out of line. If you ever take it on an airplane, you'll see how accurate (at times) the autopilot is, as the readout stays pegged at an exact altitude for minutes on end. But when driving, I find it can change by 10s of metres just moving over seemingly level ground. I was just in Florida, and the readout showed that at times I was 10' BELOW sea level and just a few yards away 10' ABOVE sea level. South Florida is, on the whole, about 10' above so the changes seemed to be strange.
I'd love to see a military unit and a civilian unit side by side.

I have seen my Nuvi 360 get to 12 feet.

Military GPS is accurate down to one centimeter.

I consistently get 12-15 foot accuracy, depending upon direction I'm traveling, how many birds I can see,and strength of the bird signals. I've not seen it below 12 feet.

12-13 feet like most outside and about 26 ft inside by my computer.

about 12 feet was the best for my Nuvi 360

DizzyFox

Driving around this evening I was consistently getting 10 foot and 11 foot accuracy.

On my Nuvi 350, the WAAS option was actually turned off by default so the first thing I did was turn this on. This should make a big difference in accuracy.

With WAAS turned on I usually get about 12 feet in accuracy.

I have experienced < 10ft with my nuvi 350 with WAAS.

That's with WAAS enabled.

I thought WAAS was not necessary with the SiRF chipset and that it wouldn't generally help at all, would cost battery life, and would slow things down. At least, that's what the various reviews have said.

WAAS is not of much help for normal driving accuracy when you have a SiRF High Sensitivity chip set.

18' here. N 660

http://gpsinformation.net/waasgps.htm has answers for WAAS questions.

I have seen accuracy down to 11-12 feet on my new Nuvi 680.

Yes, I have seen my Nuvi 350 report an accuracy of 9 Ft! I looooove my Nuvi 350!!!

And it wasn't just a once in a lifetime thing, it happens for me alot. I live in the NY metropolitan area.

but normally 10-13 on the 680 with WAAS enabled.

I had 10 feet yesterday with WASS disabled on my Nuvi 680...........Dave

I normally see 12-18 feet with the 660.

My 2610 with external antenna typically runs about 7 feet.

12 ft - nuvi 350

11 ft. That was on I-5 going south in Central California.

I don't check all that often so I don't know what it is doing most of the time, just that it seems to be keeping up with the exits, turns, bridges and stuff.

I consistently get 12-15 foot accuracy on my 660.

I went from Queens NYC by JFK Airport to Riverhead LI today, a trip of approximately 68 miles. While out in Suffolk county and the Nuvi 350 picking up all except 2 satellites and with the WAAS on the best I got was 17 feet and that was only for a few seconds, I basically got 19-20 feet for the few minutes that I was checking.

Best I have seen is 10-12 feet with WAAS on. Have not tried it off.