Ive run speed view for a few years in the mountains. Seems accurate. Here's a read out from just a few weeks ago. Not very fast unless your on a pair of snow skis.
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How accurate is vehicle speed on a GPS ?
Discussion in 'Experienced Truckers' Advice' started by bzinger, Jun 4, 2016.
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Next flight I take I'll bring along my Rand McNally, lock in the destination airport, set the speaker volume to stun, and become the passenger from hell.
"REROUTING! PLEASE TURN AROUND AS SOON AS IT'S SAFE! REROUTING! SPEED WARNING! REROUTING! SPEED WARNING! REROUTING!"Skate-Board and x1Heavy Thank this. -
My truck is gov., according to the speedo, at 77 mph. On GPS, with my buried in it on a flat, most I've seen is 76 mph.
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IF you want to see accurate than go look at Dewetron's systems, they are accurate and used for testing all over the place.
You do know that many cop radar and laser units are not accurate?
BUT one thing that I have to point out is that speedos are not meant to be close to accurate, I think the tolerance is 8% overall and that's put into US DOT regs. -
That 8 % mush in accuracy is enough to put you 15 minutes late at the wally world gaurdshack with all of your carefully laid plans for reload threatened.
You should try Speedo app on your phone and then hop the acela amtrack in the NE Corridor. If you tried to follow your train on a map online via your phone in real time, the thing will absolutely GO CRAZY showing culdesacs at 140 mph. Ever want to see a computer lose it? Ha.
There is a reason for that. Homeland security deliberately dirties up the railroad routes on GPS. In Baltimore there is a set of tracks that carry hazmat 35 yards from the main stadium there when there is no game day.
Airlines generally cruise at mach .78 or .86 or so. The actual "Ground Speed" will depend on the jetstream, your air temperature at your altitude and so on. I fly the FSX Deluxe on my computer online with People who actually are real life air controllers having some down time playing a game pushing tin into and out of approach and departure.
I will allow my self one paragraph and stick it to the US Passenger railroad system. Amtrack needs to light a fire on it's arse and frankly get some moxie and american by god horsepower and FLY on the track at 180-250 mph. None of this 125 mph crap when third world nations are cruising at 175 plus on thier rail networks. Shameful.
Im having fun with some of your postings. Keep em coming. Thank you everyone. -
REALLY?!
What is going on with these deliberate errors induced into the company truck speedometers. There has to be a bunch of money involved in savings on premiums. -
Lepton1 Thanks this.
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The speed number from your GPS is calculated by the unit itself based on the location data. It's rather simple math based on the Pythagorean theorem. With the current accuracy available (because Selective Availability is turned off,) it's very accurate. If you're seeing variations in the mountains, remember your speedometer is measure a two-dimensional speed, and GPS may be using a three-dimensional speed, although your vertical component shouldn't ever be enough to noticeably affect the speed. It's most likely an accuracy effect due to the mountains restricting your view of the sky, and thus GPS satellites. I've frankly never watched mine close enough to notice if it varies in the mountains.
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If you consider the GPS system, it generates a perfect sphere and where it intersects with another sphere generated by a satellite GPS number two, and that intersects a third sphere with GPS Number three you have now what is necessary to find the center inside those three, discarding results that point to space you have the location on the planet. If you have 4 or more GPS Satellites that can see you, the more precise you are going to be.
My head hurts if I have to understand that the vehicle speedometer is #### and it is not accurate. That's almost like living 50 years of your life and then being told your name is a lie.
Why have that #### speedometer if it's going to be crap anyway? Remember that driving 2000 miles somewhere to be JIT to the minute, preferably 15 minutes prior to appointment time arrival is ideal. The amount of deliberate error in the speed sensing and reporitng system inside the truck, dashboard and cabling etc. Is going to be enough to make you late and be told to come back tomorrow.
It's going to make me feel put out because if all this wonderful pre-cisse tech on the truck, communciations, computers and electronics made to be thrown out the window because half the Nation's 18 wheelers have #### speedos that don't work properly.
I think I better go pour a coffee and think about this some more. Maybe I grab a speedo from a Police car and throw THAT into the truck.Lepton1 Thanks this.
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