[mixR1]

Hooked to a Dyno

 

[KMac]

i dont want to burst your bubble but the commercial GPS is not all that accurate. The military installs a signal degredation. How do i know , i have installed Sperry and Honeywell GPS sys in aircraft and asked the people who actually make them.They said the military stuff is more accurate by orders of magnitude.

That used to be true, and can still be true today if the military decides to degrade the commercial signal from the satellites, which would usually be done during some kind of threat or military operation. However, the positional data is used to calculate the speed and if your positional data is off by 20 meters, it will be off by 20 meters at the next point as well. That means the delta is accurate, therefore the speed calculation is accurate.

Today, the GPS the average Joe Q. Citizen gets is much more accurate than it was 10 years ago.

Moral of the story = Manowar goes 166 mph. Period.

 

[MANOWAR]

That used to be true, and can still be true today if the military decides to degrade the commercial signal from the satellites, which would usually be done during some kind of threat or military operation. However, the positional data is used to calculate the speed and if your positional data is off by 20 meters, it will be off by 20 meters at the next point as well. That means the delta is accurate, therefore the speed calculation is accurate.

Today, the GPS the average Joe Q. Citizen gets is much more accurate than it was 10 years ago.

Moral of the story = Manowar goes 166 mph. Period.

Can't argue with logic.:bow

 

[KMac]

Can't argue with logic.:bow

Some people will. :dunno

 

[tag r 1]

That's not the way they explained it . You're assumption that you are off by 20 meters and at the next waypoint you are off by that same 20 meters is wrong.

Its calculated by a GDOP chimney. They use optimum sat's 1 ,2 , 3 , 4.
Then they compare sat's 1 ,2, 3, 5, then 1, 2, 3, 6 and so on until 8 if it's visible then covariance Kalman filter optimization and a whole bunch of other filters i'm sure.

I'm not arguing that the stuff today is better than 10 years ago because i don't know how accurate the commercial hand held stuff is . I can't speak for something i don't know. I do know that Sperry and Honeywell engineers told me that the commercial stuff is not accurate.

 

[sniper2323]

Well my garmin 76CSX claims to show a error of about 10 feet, with heavy tree cover it show between 18 and 20 feet of error. So, I would say it is very close to being on the mark, and better then the handheld GPS's I used in the military 12 years ago.

But that is just my thoughts.

 

[MANOWAR]

I'm not arguing that the stuff today is better than 10 years ago because i don't know how accurate the commercial hand held stuff is . I can't speak for something i don't know.

You just did a few post back and you just now said you don't know how accurate the commercial hand held stuff is.

 

[Skanky]

The only reason your GPS can't resolve your position/speed more accurately, is because it just can't - it would take more accurate electronics / clocks inside the GPS unit to do so.

There is no longer any "degradation" of the GPS signal any more - we all use the same satellites (that we know of).

 

[Dream_Dreas]

Probably edited his post and changed the 193 to 189....after everyone harassed him :dunno

 

[PARKER10]

Someone needs to buy a radar gun, instead of arguing about gps

 

[KMac]

That's not the way they explained it . You're assumption that you are off by 20 meters and at the next waypoint you are off by that same 20 meters is wrong.

Its calculated by a GDOP chimney. They use optimum sat's 1 ,2 , 3 , 4.
Then they compare sat's 1 ,2, 3, 5, then 1, 2, 3, 6 and so on until 8 if it's visible then covariance Kalman filter optimization and a whole bunch of other filters i'm sure.

I'm not arguing that the stuff today is better than 10 years ago because i don't know how accurate the commercial hand held stuff is . I can't speak for something i don't know. I do know that Sperry and Honeywell engineers told me that the commercial stuff is not accurate.

I don't speak from how someone "explained it to me". After several years of working with GPS based UAV autopilots, and the associated data logging from them, I can tell you from hands on, real world experience that point to point, the error is essentially the same at each point. It does change over time, and over distance, but it's not so quick that it would cause a 166mph reading to be false. IF that were the case he could hold a steady 166 and his GPS would be displaying changing speeds that the bike couldn't possibly achieve. All of this data can be backed up through parallel use of differential GPS.

 

[04R1UK]

also between the current R1 and CBR1000RR there realy isnt anything in it performance wise, ive ridden the 2006 R1 and own the CBR there pretty much equal in performance terms

 

[bender]

Hooked to a Dyno

I'm really surprised that no one else picked this up too. I've done alot of riding at speed, and the way his engine is howling just screams that it's on a dyno. He certainly wasn't on the road when he took the video of this.

With a good tailwind speeds higher that 186mph are attainable on a near stock R1.

 

[madmathew]

Nobody has brought up aerodynamics either. The new issue of Sport rider has a good article on this. Once again the rider makes a huge difference.

 

[plinss]

I don't speak from how someone "explained it to me". After several years of working with GPS based UAV autopilots, and the associated data logging from them, I can tell you from hands on, real world experience that point to point, the error is essentially the same at each point. It does change over time, and over distance, but it's not so quick that it would cause a 166mph reading to be false. IF that were the case he could hold a steady 166 and his GPS would be displaying changing speeds that the bike couldn't possibly achieve. All of this data can be backed up through parallel use of differential GPS.

You are correct, put two GPS units next to each other and they will both show the same error (within a very small margin, generally around 1cm). The farther away in distance or time the two units are, the larger the error.

This is how differential GPS works, one GPS receiver sits at a known location, it measures where it thinks it is by GPS, then broadcasts the difference (ie: the "differential signal") to other units around it, they subtract this difference from the position they read and know where they really are very accurately.

A commercial GPS, even an older one, is generally accurate measuring "steady state" speed to better than 0.1 mph. This is true even with selective availability turned on (selective availability is where the military scrambles the low order GPS signal to introduce an error that they can correct for, because they have the encryption key). Even when there's an error, the error is consistent from one reading to another.

Note that the specs say "steady state" speed, ie: going the same speed over time, in a straight line. The error will be larger when accelerating or turning because the GPS is not sampling fast enough to keep up with the changes.

 

[TheBFA]

The only reason your GPS can't resolve your position/speed more accurately, is because it just can't - it would take more accurate electronics / clocks inside the GPS unit to do so.

There is no longer any "degradation" of the GPS signal any more - we all use the same satellites (that we know of).

I don't know of any degredation, but I know that commercial stuff is not as accurate as military units CAN get. I am a Seahawk crewman, and stare at a multifunctional display quite a bit while performing antisubmarine operations. Our GPS, which selects up to 5 satellites, is generally running 16-32 YARDS of EHE (estimated horizontal error). 8 yards of horizontal error is the best our military grade GPS units on the helicopter will go, UNLESS we switch over to using classified transmissions, which we've never bothered doing for the GPS, but have done quite a bit over radio. I can't disclose how accurate they are, but it's not necessarily pin point accuracy.

I highly doubt that commercial grade have 20 FEET of error in them. I would say more like 20 yards at best. The statement of 20 feet of error is the same 20 feet of error is not correct. The error is not linear. If the device knew it was 20 feet off in one direction, don't you think it would be able to correct for it and give you the exact point? The error is spherical, and the "20ft" is the radius. It's saying you are somewhere in that sphere of error. So if you moved 20 ft in a straight line, the GPS could read that you didn't move at all, or moved 80ft, based on the max error in opposite directions. The error even changes. While looking at my MFD, I constantly see the EHE changing. I would say it changes every second. I've even seen it get over 100 yards of estimated error.

 

[cyclepsycho7]

Looked like 189 o me:dunno

:iamwithst

 

[Skanky]

Does anyone know how often most commercial GPS systems sample positions to determine speed?

I'm guessing that at near 200MPH, the inaccuracy of GPS is extremely insignificant. Meaning, that if the GPS reads 193 MPH, it probably was 193 MPH.

 

[plinss]

I don't know of any degredation, but I know that commercial stuff is not as accurate as military units CAN get. I am a Seahawk crewman, and stare at a multifunctional display quite a bit while performing antisubmarine operations. Our GPS, which selects up to 5 satellites, is generally running 16-32 YARDS of EHE (estimated horizontal error). 8 yards of horizontal error is the best our military grade GPS units on the helicopter will go, UNLESS we switch over to using classified transmissions, which we've never bothered doing for the GPS, but have done quite a bit over radio. I can't disclose how accurate they are, but it's not necessarily pin point accuracy.

I highly doubt that commercial grade have 20 FEET of error in them. I would say more like 20 yards at best. The statement of 20 feet of error is the same 20 feet of error is not correct. The error is not linear. If the device knew it was 20 feet off in one direction, don't you think it would be able to correct for it and give you the exact point? The error is spherical, and the "20ft" is the radius. It's saying you are somewhere in that sphere of error. So if you moved 20 ft in a straight line, the GPS could read that you didn't move at all, or moved 80ft, based on the max error in opposite directions. The error even changes. While looking at my MFD, I constantly see the EHE changing. I would say it changes every second. I've even seen it get over 100 yards of estimated error.

You are not taking WAAS into account. Any WAAS capable GPS in North America will be accurate to 7 meters 95% of the time. In real world use, most WAAS enabled devices will be accurate to 2-3 meters most of the time.

Your military unit most likely is not WAAS capable or is not operating in an area serviced by WAAS.

With selective availability turned on and WAAS turned off, commercial GPS units will only be accurate to 100 meters. With selective availability turned off, or a military GPS capable of decoding the encrypted data, accuracy will improve to 15 meters RMS 95% of the time.

The only way to get more accurate, is to use some kind of differential signal. This is due to the basic physics of the GPS signals, and no "better" GPS receiver can improve on it.

WASS is one kind of differential signal, I'm sure the military has better differential hardware to improve GPS accuracy in any given theater. Even civilian grade differential GPS hardware can achieve accuracy down to 1cm in close proximity.

There is no need to be guessing or second guessing here, there are plenty of cold hard facts available about the GPS system to anyone who wants to look.

 

[plinss]

Does anyone know how often most commercial GPS systems sample positions to determine speed?

I'm guessing that at near 200MPH, the inaccuracy of GPS is extremely insignificant. Meaning, that if the GPS reads 193 MPH, it probably was 193 MPH.

It varies by unit, my older unit a Garmin GPS III+ samples once per second. But even that unit can accurately measure speed to about .1 mph.

Directly from the manual:
Velocity Accuracy: 0.1 knot RMS steady state

This means, as I've said before, if you're traveling in a straight line, at a constant speed, your GPS will display your speed accurately to 0.1 knot (ok, 0.1152 MPH)

This figure already takes into account the positional accuracy of the GPS. And for the most part, the positional accuracy does not matter when measuring speed, because the positional error will not vary from sample to sample by a large enough factor.

So yes, bottom line, if the GPS says 193, it was 193 to within a small margin of error. Much more accurate than any speedo.