The True Speed of your GS 500

[peterscotts]

I did a GPS check of the speed, using a Garmin nuvi 2455LM..

I found at 80 kmh on the Suzuki GS 500 ...

I was actually going 74 kmh...

And at 90 kmh I was really doing 83 kmh at 100 kmh I was doing 92 kmh ..

So I would think at 110 kmh , it would be doing 101 kmh and at 120 kmh you'd be going 110 kmh


Thoughts  

[sledge]

Yep......over indicating by about 10%

Don't worry about it, they all do it 

[Janx101]

i know a while back.. while i was testing with a nuvi also (car one but) .. yes i got similar results...

and when i got the needle to coughcoughcough195coughcoughcough ... i was way too friggin busy and tucked down on the tank too much to try twisting my head sideways to check the actual readout! 

.. edit... s'funny though... on a friends TL100R years ago.. i was ... doing more than that  ... and it didnt FEEL as fast? .... maybe cos it just got there so damn quick!! .. never had time to comprehend/contemplate the scenery rushing by as much ... ?? 

[peterscotts]

Yep......over indicating by about 10%

Don't worry about it, they all do it 

Spot on Sledge...

Heard about the 10% over the years...

The little 4 cyl car is the same.

Hey Sledge...

You'd know , would the big bikes Harley's.. Triumph's and a like, you know the big cruisers 16.. 1700's to the 2.3 ltr they'd be more to the real wouldn't they   

[peterscotts]

i know a while back.. while i was testing with a nuvi also (car one but) .. yes i got similar results...

and when i got the needle to coughcoughcough195coughcoughcough ... i was way too friggin busy and tucked down on the tank too much to try twisting my head sideways to check the actual readout! 

.. edit... s'funny though... on a friends TL100R years ago.. i was ... doing more than that  ... and it didnt FEEL as fast? .... maybe cos it just got there so damn quick!! .. never had time to comprehend/contemplate the scenery rushing by as much ... ?? 

     

[sledge]

Hey Sledge...

You'd know , would the big bikes Harley's.. Triumph's and a like, you know the big cruisers 16.. 1700's to the 2.3 ltr they'd be more to the real wouldn't they   

Assuming they are using analogue clocks I doubt it. Construction and use regulations throughout the world are more or less the same and generally state speedos can have a tolerance of  +10% - 0%. In other words they are allowed to over read but never under read.

Of course the manufacturers could easily  fit more accurate speedos but the upshot is they would cost more. 

Make yourself a coffee, kick back and have a read through this........ 

http://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/r039r1e.pdf

[slipperymongoose]

I've never been a fan of using GPS to measure speed due to positioning of satellites etc. in order to get an accurate read on your speed you need at least 3 satellites over you. And guess who controls the GPS satellites? That's right the US military

[Janx101]

I've never been a fan of using GPS to measure speed due to positioning of satellites etc. in order to get an accurate read on your speed you need at least 3 satellites over you. And guess who controls the GPS satellites? That's right the US military

Hmmm yeah I guess... But Uncle Sam cares if I'm being a hoon somewhere in a Aussie back road? ...

With the Garmins you can call up a screen that tells you all of the satellites available ... Seem times up to 13!! .... It automatically chooses the best 3 and there is a recurring self check routine in there too.... Most car gps do this ...

But if GPS freak you out .... You carry a mobile phone yeah?? ... Wellllll....... 

[slipperymongoose]

Don't get me wrong I love using GPS I just don't rely on it for speed reference.

[Janx101]

Don't get me wrong I love using GPS I just don't rely on it for speed reference.

Yeah true I guess... But I have tested mine with every road info radar set I could find ... Plus a friendly constable that I kinda know .. +/- 1kph ... And the only thing that is commonly more accurate for road purposes is police handheld laser unit.. +/- 0.5kph ... Which is what 'tested' my gps ...

In an odd twist though ... My little turbo diesel 4wd ute , after the 15"rims and larger tyres went on ... The speedo now reads 97-98k when GPS says 100k .. I didn't have the GPS for a while after the tyre change ...  Still assumed the speedo was optimistic ... Cruised past a lot of cops doing 108k  on the needle .. Got a few hard stares but no hassles ... Most of the time the cops are looking for serious speeders ... But I don't rely on that ..

Downhill/uphill change it also by 1-2kph .... As do a lot of curves in the road... You get about 1-3% 'lag' out of it...

Oh and the cousins worked over gtr32 .... That just accelerates faster than the GPS can keep up

[Leadberry]

I've never been a fan of using GPS to measure speed due to positioning of satellites etc. in order to get an accurate read on your speed you need at least 3 satellites over you. And guess who controls the GPS satellites? That's right the US military

Perhaps you don't understand how GPS speed calculations work.  For most modern automotive GPS receivers, the Doppler shift in the signal waves between the satellite and the receiver is used to calculate average speed over an extremely small time interval--small enough to be considered an instantaneous speed measurement for practical purposes.  Doppler shift can be measured with extreme precision and sensitivity--it relies on the velocity of the satellite and the velocity of the receiver.  Up through the 90's, the DoD intentionally degraded civilian GPS signal carrier waves; this was the main source of error in all calculations.  However, this signal quality reduction has long since been terminated and any interference is now almost entirely atmospheric.  Accuracy of modern systems has been shown time and again to be +/- 0.1 - 0.2 m/s over a relatively straight path.  Small-radii turns and abrupt acceleration can reduce accuracy somewhat.

If your distrust of GPS is politically motivated, note that if DoD degrades the civilian signal, ALL systems which use this signal are affected.  This includes public transit, shipping vessels, commercial fleet trucks, surveying equipment, farm equipment, etc.  The civilian signal degradation was shut down specifically because so many entities both in the US and worldwide have grown reliant on GPS for efficient and reliable operation.  In other words, they aren't going to mess with the signals to screw with some motorcyclist's speed measurements.

[slipperymongoose]

Tell you what go out and get caught speeding while using your GPS and stand infront of the judge and argue to him that your gps is more accurate than a police radar.

[Leadberry]

Tell you what go out and get caught speeding while using your GPS and stand infront of the judge and argue to him that your gps is more accurate than a police radar.

Who ever stated that GPS was more accurate than radar?  They use the same concepts to calculate speed.  Besides, if your GPS tells you you're speeding, then you're speeding.  I'm not quite sure I understand the argument you're trying to make.  o.O

[twocool]

Wow!   That's all I can say, Wow!

Oh, OK, I can say more.........yes, you've stumbled on yet another Obama scandal...the conspiracy.....by the US government to screw up motorcyclists all over the country...by applying the "military dither" to the GPS, thus making our GPS speed readings totally inaccurate!   Oh the humanity!



Cookie

I've never been a fan of using GPS to measure speed due to positioning of satellites etc. in order to get an accurate read on your speed you need at least 3 satellites over you. And guess who controls the GPS satellites? That's right the US military

[slipperymongoose]

Guess the point I'm making is if a cop pulls you over for doing 1mph over the limit (he feels like being a complete c@%t this particular day) but your gps says your doing the limit. And you somehow document this, and take the ticket to court I have a feeling the judge will believe the policeman with his speed measurement device over your gps.

And as for government conspiracy it's a fact GPS was developed for the US military and they have control over the satellites. The advantage of this is if your using your gps in Iraq or Afghanistan or Pakistan or Iran (any warzone or area of US interest pretty much) your signal will be very powerful and very accurate. As for your humble gps in your car in the middle of bumfuck Arizona sure its gonna work great bouncing of at LEAST 1 satellite but personally I (and this is my opinion) wouldn't fully trust the speed it tells me I'm doing.

[peteGS]

Something not many people know yet is that they changed the ADR's over here in Aus... it used to be your speedo could read +/- 10% and be fine.

Now, however, your speedo can over read by 10% (ie you can be doing 10% less than what your speedo says) but it can not over read at all. So if your speedo says 60 and you're doing 61, it's now a breach of the ADR. I had a link to the paragraph once but lost it...

When I replaced my analog stock gauges with the Acewell I used an external GPS device with my work iPhone to confirm calibration after measuring my tyre diameter, and I set it so that when my speedo says 60 I'm doing 57... just to give me some breathing room.

I've done 65 through a radar and they didn't even blink an eye... I reckon that means my GPS calibration was pretty good 

[Wagoneer]

I have to watch myself switching back and forth between my bike and car. I have 28" tires on my car that came stock with 25.7" tires so it reads about 8km/h slow and my bike reads high. Both have GPS so I try and stick to that speed (you know, when I'm trying to actually go the speed limit).

[twocool]

Bottom line...for speed...GPS is EXTREMELY accurate.....Garmin claims plus or minus 1/2 MPH (if ALL errors add up in the same direction)...usually the accuracy is more like within 7 one hundredths of a MPH...and can go as low as to one one hundredth of a MPH......


Since most car units read out speed in even MPH or KPH...you gotta figure plus or minus 1/2 MPH or KPH..........

Police radar or laser is also EXTREMELY accurate..  But the system is designed such that any possible error always goes in favor of the driver......biggest problem is when the cop is shooting the radar at an angle to the oncoming car...within say 10 degrees it is still accurate...as you go beyond 10 degrees the radar will read low, in favor of the driver....

Which is more accurate, GPS or Radar? ....I dunno, and for our purposes it doesn't matter........because one MPH increments are fine for whatever we are doing........

As for speedometers...especially on motorcycles...they are KNOWN to be very inaccurate ...  to the tune of 8% to 10%.........Again they always go to the conservative....

Motorcycle speedos ARE fairly precise however...so it would be a simple matter to CALIBRATE your speedo...and get reliable accurate readings...........You could just apply a 10% correction...for easy calculation in your head........so if it reads 60 you're really going 54...etc....

I saw somewhere where some guy was making new dials for MC speedos....he simply printed the numbers in the correct places so as to give very accurate readings......

Now...operator error can f up anything.....so if the cop is an idiot, and shoots the speeding car next to you, but thinks it is you who is speeding, when you are not...then you have a big problem....I don't know of many (any) cases of cops citing someone for going 1 mph over the limit....but I guess they could be a Pr--ck...

Also...I agree...don't ever trust the government.......power corrupts etc...

And yes the military has the ability to F-up the gps system, so as to throw off the enemy....

But since the Russians have a complete satellite system which mirrors ours, and most modern GPS units can see the Russian satellites as well as the US satellites....it is hard to get bad readings anymore.........(My newest gps receiver can monitor up to 48 satellites at once.......)

Also GPS now uses WAAS and "differential GPS"...which can easily sort out possible errors in the system........Since airplanes now routinely use GPS for "instrument" approaches.....they don't F up the gps system since it would result in lots of planes missing the runways on landing...

Cookie

Guess the point I'm making is if a cop pulls you over for doing 1mph over the limit (he feels like being a complete c@%t this particular day) but your gps says your doing the limit. And you somehow document this, and take the ticket to court I have a feeling the judge will believe the policeman with his speed measurement device over your gps.

And as for government conspiracy it's a fact GPS was developed for the US military and they have control over the satellites. The advantage of this is if your using your gps in Iraq or Afghanistan or Pakistan or Iran (any warzone or area of US interest pretty much) your signal will be very powerful and very accurate. As for your humble gps in your car in the middle of bumfuck Arizona sure its gonna work great bouncing of at LEAST 1 satellite but personally I (and this is my opinion) wouldn't fully trust the speed it tells me I'm doing.

[slipperymongoose]

Good to know the system has been upgraded and the ruskies have a system too. I know the GPS is fairly on the money I never said its so far out its bit funny but once as a laugh I used 2 GPS, 2 iPhones and reading my car speedo and found the iPhones read the same speed, the gps's gave different readings (about 4km/h difference) and that my car speedo is a bit on the conservative side which is fine by me cause I like my licence. With that info which do you believe? Which is where I base my opinion on of not fully trusting a GPS for my speeds.

Here's a fun fact. The iPhone has a built in function apparently to automatically shut down once it reaches 2.5 times the speed of sound in case it is being used as a missile guidance system. Apparently.

[Janx101]

From what I have seen of documents ..

For enforcement purposes ...

Laser 0.5 km/h accurate ,800 m scan, 600-400m usual active track range

Ka band (slant radar) , 1-3km/h accurate 150m? Scan 10-40 m usual active track range (not as popular as when they first came out.. Thankfully)

K band 2-5 km/h accurate, 500-600m scan, 300-100m usual active track range

X Band (old and clunky) 7-10km/h accurate, 300-500m scan, 350-150m usual active track range

Mk 1 police eyeball ... 'Apparently everywhere' ... 'Always accurate' ... 'See around corners and over hills?' .... Often associated in the old days ... With the police boot up the arse!