Miles Per Hour Number on Nuvi 880

 

My Nuvi 880 gives a MPH number that is about 5 mph slower than the odometer on my 2008 BMW 328. I assume that German engineering is more accurate than a Chinese made device but that may be cultural prejudice. I hope the Garmin is more accurate so I can go faster. grin

Any thoughts?

go with the Nuvi

My thought is the speedometer is fast on most cars. 5 is more than usual however.

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1490LMT 1450LMT 295w

Miles Per Hour

On my truck the speed is exactly the same mph. My wife's car is 5 mph over the garmin's speed.

My opinion - Garmin is more accurate

Garmin gives me a number that is about 2 mph slower than my Honda. I have checked the speedometer at measured miles on state roads and at police radar trailers that display speed, and the Garmin is exactly right.

dobs108 - Garmin nuvi 760 smile

cwr wrote: My Nuvi 880 gives

cwr wrote:

My Nuvi 880 gives a MPH number that is about 5 mph slower than the odometer on my 2008 BMW 328. I assume that German engineering is more accurate than a Chinese made device but that may be cultural prejudice. I hope the Garmin is more accurate so I can go faster. grin

Any thoughts?

I have a Garmin 1450 and it seems to be off just a mile or two per hour,one thing you have to look out for is the speed limit signs many times on my unit it say 70 mile an hour zone when it might be a 55 or 60 mile an hour zone.

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The GPS will always be correct.

Yes, you can now go faster, but your buffer zone for tickets is now also smaller.

Your tire profile (aspect ratio) will play a part in the speedo/ GPS accuracy as well.

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nüvi 3790T | Those who make peaceful revolution impossible, will make violent revolution inevitable ~ JFK

mph and nuvi

interesting, i would've though the speedometer is more accurate, but then again with gps we're talking satellites locked in on u and all that math algorithm.

nuvi vs speedometer accuracy

has been discussed at length in other threads in this forum. Here are a couple of them:
http://www.poi-factory.com/node/26671
http://www.poi-factory.com/node/6695

You can easily check your speedometer accuracy. Here is a copy of a post from one of the above threads that describes how to do it:

alandb wrote:

If you live close to a stretch of highway with mile markers, it is easy to check your speedometer or GPS speed accuracy using only a stopwatch or even a watch with a second hand. The process is simple. On a calm day, find a flat, strait stretch of road where you can set your cruise control and not have to slow down or pass for 4 or five miles. Use a stopwatch to capture the time starting at the instant you pass a mile marker and stopping as you pass another marker 4 or 5 miles down the road. The formula is:

(distance X 3600) / (time in seconds)

So if you drive 5 miles in 4 minutes 28 seconds, that is a total of 268 seconds and your speed is

(5 miles X 3600) / 268 seconds = 67.16 MPH.

I have found you can get a pretty accurate speed reading in just 1 mile, but if you can hold a constant speed for 4 or 5 miles, you can get a very accurate speed calculation. Note that this formula will work equally as well in kilometers per hour assuming you can find kilometer road markers. For both accuracy and safety reasons, I recommend that you have a passenger watch the mile markers and operate the stop watch.

I have used this method several times and I find my Garmin 755T speedometer is right on. My 08 Elantra speedometer is consistently about 2 MPH fast at 60 MPH.

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Alan - Android Auto, DriveLuxe 51LMT-S, DriveLuxe 50LMTHD, Nuvi 3597LMTHD, Oregon 550T, Nuvi 855, Nuvi 755T, Lowrance Endura Sierra, Bosch Nyon

Garmin speed = radar detector speed

My experience: Garmin/garmin fone/iPhone speed = radar detector/camera speed. My odometer alway gives 1 or 2 mph faster.

tires

Tire size and pressure has some to do with it....

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Being ALL I can be for HIM! Jesus. Kenwood DNX9980HD Garmin 885t

mine

is 5 MPH slower for all my cars.

I Get Varying Readings

Between the speedometer on my 2009 Camry and my Nuvi 760, the difference is NOT linear. The car reads about 5mph faster below 35mph. The readings get closer until they match from 40 to 45, then the car starts reading faster again. At about 50 it's a 5mph difference again.

Garmin Vs German engineering

cwr wrote:

My Nuvi 880 gives a MPH number that is about 5 mph slower than the odometer on my 2008 BMW 328. I assume that German engineering is more accurate than a Chinese made device but that may be cultural prejudice. I hope the Garmin is more accurate so I can go faster. grin

Any thoughts?

Your Garmin has nothing to do with Chinese engineering-it is the satellites in space that figure your position. The Garmin is correct.

The car manufacturers

The car manufacturers decided long ago that to err on the high side of speed was to encourage drivers to drive slower. If they ever had the error the other way around, it could make them vulnerable to law suits. I've rarely found a car that was dead on with respect to speed & the error was always on the high side.

Fred

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dup

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Currently have: SP3, GPSMAP 276c, Nuvi 760T, Nuvi 3790LMT, Zumo 660T

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GPS is in general very accurate - but you will notice variations from time to time owing to multipath, atmospherics as well as the civilian algorithm. That's why your unit will 'wander around' a bit when stationary.

It isn't the car manufacturers, but rather the law which requires that speedometers on passenger vehicles be either accurate or optimistic.

They are not allowed to read lower than the actual driving speed.

Clearly if they wanted to they could make them all 'spot on', but I suspect they don't simply because of their cost for calibrating each and every vehicle. Plus, as has been pointed out, the values are affected by tire size and wear.

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Currently have: SP3, GPSMAP 276c, Nuvi 760T, Nuvi 3790LMT, Zumo 660T

Trust GPS

When it comes to issue of the speed that you are going I trust the GPS. Remember this is being calculated by using satellite accuracy (an not just tire pressure/worn out speedo cable in the car.

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Garmin c340 265WT 1490T 295W 2460LMT 2555LMT 2757LM

The GPS Is Correct

But the GPS is only accurate when traveling in a straight line on level ground.

Consider the situation where you are driving 30 MPH in a tight circle. The GPS checks your position every one second. If you happened to be in the same location every time the GPS checked your position, it would report your speed as zero. In more gradual turns, the GPS will always report your speed lower than actual speed.

If you were traveling eastbound up a steep hill at 30 MPH, your easterly speed across the globe would always be less than that. SO the GPS would once again report a lower than actual speed.

Rick

@RickLeb

I found my old TI-30 calculator. If your speedometer was calibrated perfectly and you were ascending a 6% grade (really steep for Interstate) the nuvi would show 60 mph and your car 60.3.

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1490LMT 1450LMT 295w