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 :icon_question: :dunno_black:
Yep......over indicating by about 10%
Don't worry about it, they all do it :thumb:
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! :icon_rolleyes: :icon_twisted:
.. edit... s'funny though... on a friends TL100R years ago.. i was ... doing more than that :icon_rolleyes: ... 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 ... ?? :angel:
Quote from: sledge on June 02, 2013, 11:54:33 PM
Yep......over indicating by about 10%
Don't worry about it, they all do it :thumb:
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 :icon_question: :dunno_black:
Quote from: Janx101 on June 02, 2013, 11:59:02 PM
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! :icon_rolleyes: :icon_twisted:
.. edit... s'funny though... on a friends TL100R years ago.. i was ... doing more than that :icon_rolleyes: ... 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 ... ?? :angel:
:icon_lol: :laugh: :) :angel:
Quote from: peterscotts on June 03, 2013, 12:11:00 AM
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 :icon_question: :dunno_black:
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. :dunno_black:
Make yourself a coffee, kick back and have a read through this........ :thumb:
http://www.unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/r039r1e.pdf
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
Quote from: slipperymongoose on June 03, 2013, 01:37:41 AM
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....... :icon_rolleyes:
Don't get me wrong I love using GPS I just don't rely on it for speed reference.
Quote from: slipperymongoose on June 03, 2013, 02:28:12 AM
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 :icon_eek: .. 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
Quote from: slipperymongoose on June 03, 2013, 01:37:41 AM
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.
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.
Quote from: slipperymongoose on June 03, 2013, 03:40:36 AM
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
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!
:cookoo:
Cookie
Quote from: slipperymongoose on June 03, 2013, 01:37:41 AM
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
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.
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 :thumb:
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).
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
Quote from: slipperymongoose on June 03, 2013, 04:05:53 AM
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.
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.
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! ;)
Oh, Now I know why my i phone shut down yesterday when I was really pushing the GS...
I have been told, but have no way to know for sure, that the GPS in phones is not as good as stand alone GPS units........also early phones used a different system for positioning, not gps, but position related to cell towers.....
There is lots of navigation apps for flying available for i phone or android tablets...but most pilots do not use the "internal" GPS in these devices.....but rather feed in the GPS signal from a "better" dedicated GPS unit.......
technology is moving really fast so who knows anymore.....
Cookie
Quote from: slipperymongoose on June 03, 2013, 05:45:09 AM
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.
Lol two cool .... Using hi octane again are ya? ;) :thumb:
Rocket fuel...
Quote from: Janx101 on June 03, 2013, 06:02:45 AM
Lol two cool .... Using hi octane again are ya? ;) :thumb:
yeah...this is why a cop is not gonna cite you for 1 over the limit...it will not stand up in court....
Every time I have been stopped for speeding...guess what...I WAS speeding....almost every time the cop let me go ...(I suddenly get very polite when I get stopped)
One time however, I was driving thru South Carolina in my 1966 VW micro bus.....the state troopers has set up a speed trap, and they pulled over an entire line of about 12 cars.....I was about #6 in line..........one by one the cops worked their way back, giving out speeding tickets....when they got to me....and said I was doing 75 in a 60 zone...I said..."officer....this vehicle is incapable of going 75....the top speed is 58 MPH....you can take a ride with me and I'll show you"...the officer took a couple steps back....eyeballed my beat- o-crap van...and came back with a "warning" not a ticket.........later I discovered some slack in the accelerator cable, and was able to attain 60 MPH!
Cookie
Quote from: Janx101 on June 03, 2013, 05:59:07 AM
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! ;)
Quote from: peteGS on June 03, 2013, 04:36:18 AM
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.
Shouldn't that be `under`?
Quote from: slipperymongoose on June 03, 2013, 04:05:53 AM
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.
On my phone so this will be short. Once again nobody said GPS was more accurate than radar. Also we've already stated a peak error of 1 mph so you should know you could be speeding. If you really want to get into that, most jurisdictions would never uphold a ticket for 1 mph over these days as it's too hard to hold up in court.
Second, we already acknowledged satellites are owned by DoD. Nobody is disputing that. Satellites are put into orbit and then they are left to drift. We can't just fly them to a war zone. They're overhead or they're not. As an electrical engineer, I fail to see how this allows resolution to be selectively "very powerful" in war zones.
The only point anyone has tried to make is that GPS speed readouts are extremely accurate. No one claims it to be more accurate than radar or LiDAR--you're arguing with yourself there. Your technical understanding of GPS is plain wrong. :P
Quote from: slipperymongoose on June 03, 2013, 04:05:53 AM
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.
It's also a fact that worldwide commercial aviation has become so dependent upon GPS that the US DOD would have to have an awful good reason to mess with the performance of the system anywhere on the planet. While they are more than capable of messing with you, and by "you" I mean degrading or denying service in a specific region, there is virtually zero chance that they are or ever will outside of a war zone.
Nominal commercial grade GPS performance is generally better than about 1 m/s or about 2 MPH. GPS performance will be degraded under difficult reception environments including dense tree cover, tall buildings, and the like.
Could switch to a digital gauge and just not worry about it. Lol...closed circuit means no outside interference. And remember, dangle tin foil from the forks and the police radar doesn't work. :icon_mrgreen:
Quote from: Leadberry on June 03, 2013, 08:31:33 AM
Quote from: slipperymongoose on June 03, 2013, 04:05:53 AM
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.
On my phone so this will be short. Once again nobody said GPS was more accurate than radar. Also we've already stated a peak error of 1 mph so you should know you could be speeding. If you really want to get into that, most jurisdictions would never uphold a ticket for 1 mph over these days as it's too hard to hold up in court.
Second, we already acknowledged satellites are owned by DoD. Nobody is disputing that. Satellites are put into orbit and then they are left to drift. We can't just fly them to a war zone. They're overhead or they're not. As an electrical engineer, I fail to see how this allows resolution to be selectively "very powerful" in war zones.
The only point anyone has tried to make is that GPS speed readouts are extremely accurate. No one claims it to be more accurate than radar or LiDAR--you're arguing with yourself there. Your technical understanding of GPS is plain wrong. :P
Nah my understanding of GPS is just fine thanks the entire time you missed my point of saying in my opinion I don't trust the speed readings of GPS. Aaaaand at least in the early days of the system the satellites orbit could be changed so there was always a more powerful signal over war zones for help the yanks out. Nowadays with the Russians having their system plus the American system the coverage over the earth is probably decent enough to let them float.
And here's a question for ya mr electrical engineer. If the GPS is that good why havnt car manufactures replaced speedos in cars with ones that read from GPS instead of traditional ways?
Quote from: slipperymongoose on June 03, 2013, 01:50:14 PM
And here's a question for ya mr electrical engineer. If the GPS is that good why havnt car manufactures replaced speedos in cars with ones that read from GPS instead of traditional ways?
Because they only work in the plains. As soon as your on a hill, up or down, your traveling the hypotenuse of the angle while the GPS is only calculating for the adjacent distance. Plus the fact that it doesn't work in the mountains.
(http://revisionworld.co.uk/sites/default/files/imce/trig.gif)
Good enough for me.
Quote from: Leadberry on June 03, 2013, 08:31:33 AM
Satellites are put into orbit and then they are left to drift. We can't just fly them to a war zone. They're overhead or they're not. As an electrical engineer, I fail to see how this allows resolution to be selectively "very powerful" in war zones.
I read that they can move the orbit of the gps, so conceivably they could be moved to better cover a warzone - however as you mentioned there's still the problem that it will only pass directly overhead once every 12 or so hours. (The geography of the land would determine the actual time for line of site between the satellite and the "warzone")
In any case the current system on average has line of site to 9 satellites from any point on earth; even if they did shift a satellite, I doubt there would be any benefit to having 10 satellites overhead instead of 9.
As for the military's higher resolution, I've heard before and wikipedia agrees that the military gets better GPS resolution by using robust military equipment which runs off a separate, encrypted signal to the civilian signal. Which from a conspiracy theorist's point of view means yes, the US military could* turn off GPS for everybody but themselves (and whoever can crack the encryption).
*probably won't
You are not gonna drive a GS500 on a hill steep enough to make any noticeable difference....
Some GPS can measure in three dimension....Auto type usually just project your position on a conceptual surface of the earth, ignoring the ups and downs......but again still extremely accurate since we can't (or don't) ride up a grade of more than about 6%..
No matter how suspicious you are...GPS is still extremely accurate..........
Car speedos are (can be) very accurate too..........
I had an electronic speedo on my honda elite scooter 1984.......also had a gps on it...both read exaclty the same at all times......
Aviation has gone for GPS in a really big way...I guess the auto makers are still a bit behind.....
If I ever get around to building the Bobber I have in mind...the only instrument on it will be the smallest GPS I can find.......no tach, no speedo, no indicator lights etc....
Cookie
Quote from: Slack on June 03, 2013, 03:43:13 PM
Quote from: slipperymongoose on June 03, 2013, 01:50:14 PM
And here's a question for ya mr electrical engineer. If the GPS is that good why havnt car manufactures replaced speedos in cars with ones that read from GPS instead of traditional ways?
Because they only work in the plains. As soon as your on a hill, up or down, your traveling the hypotenuse of the angle while the GPS is only calculating for the adjacent distance. Plus the fact that it doesn't work in the mountains.
(http://revisionworld.co.uk/sites/default/files/imce/trig.gif)
Quote from: twocool on June 03, 2013, 05:33:49 PM
You are not gonna drive a GS500 on a hill steep enough to make any noticeable difference....
Some GPS can measure in three dimension....Auto type usually just project your position on a conceptual surface of the earth, ignoring the ups and downs......but again still extremely accurate since we can't (or don't) ride up a grade of more than about 6%..
No matter how suspicious you are...GPS is still extremely accurate..........
Car speedos are (can be) very accurate too..........
I had an electronic speedo on my honda elite scooter 1984.......also had a gps on it...both read exaclty the same at all times......
Aviation has gone for GPS in a really big way...I guess the auto makers are still a bit behind.....
If I ever get around to building the Bobber I have in mind...the only instrument on it will be the smallest GPS I can find.......no tach, no speedo, no indicator lights etc....
Cookie
Quote from: Slack on June 03, 2013, 03:43:13 PM
Quote from: slipperymongoose on June 03, 2013, 01:50:14 PM
And here's a question for ya mr electrical engineer. If the GPS is that good why havnt car manufactures replaced speedos in cars with ones that read from GPS instead of traditional ways?
Because they only work in the plains. As soon as your on a hill, up or down, your traveling the hypotenuse of the angle while the GPS is only calculating for the adjacent distance. Plus the fact that it doesn't work in the mountains.
(http://revisionworld.co.uk/sites/default/files/imce/trig.gif)
No doubts about the benefits of GPS. When john cleese my satnav voice tells me to turn left in 300m his bang on or just about. I love having the odd satnav race to. But since doing my gps comparrasion I take the speed readouts with a grain of salt.
I would love to add my two cents here as a road rally competitor (in cars) I have seen a huge difference in the various speed measurement instruments available. I drive an older car that uses a mechanical cable driven input from the gearbox and it is fairly accurate..up to 35mph, after that you start to get slippage of the gears (spinning on the input shafts) on the inside of the speedometer. Some are better than others but they all have a deviation.
The international standard regarding how much vehicle speeds can be off was put into effect in the late 80's if I remember correctly (65 on my 1983 car speedo is closer to 70 actual) so I missed out on that by a few years. GPS is accurate speed and distance wise only if you are traveling in a fairly straight line without any quick direction changes (switchbacks anyone? :icon_mrgreen: , those can alter readings by a few 10ths of a mile and momentarily throw speed readings. GPS also suffers from line of sight signal reception issues, if you are in the mountains and there are no satellites directly above, you loose signal accuracy and it starts to guess on your speed and direction based on last known direction and speed; or it cuts out entirely.
I use a purpose made rally computer that reads pulses off the hub of an un-driven wheel of my car and they display speed to a 10th and distance down to the 100th of a mile (or km if you like). It still can be thrown off by wheel slip of course but it is the answer to GPS inaccuracy and can easily be tuned for different wheel and tire sizes.
I think for all intents and purposes a dedicated Gps more than fits the average riders needs.
Quote from: BrianRC on June 03, 2013, 10:47:25 PM
I would love to add my two cents here as a road rally competitor (in cars)
I use a purpose made rally computer that reads pulses off the hub of an un-driven wheel of my car and they display speed to a 10th and distance down to the 100th of a mile (or km if you like)..
Yes please do!! .. rally!!! :thumb:
.... :icon_eek: ... want that puter!!! ... :icon_mrgreen:
Quote from: BrianRC on June 03, 2013, 10:47:25 PM
I would love to add my two cents here as a road rally competitor (in cars) I have seen a huge difference in the various speed measurement instruments available.
f%$k what have I started here...
The GPS is useless once your in a tunnel which are in the major cities (looses satellite) also not much good in major cities as in the heart of the city because of all the tall building... Again looses the satellite. :technical:
You got a beauty here havnt had this much fun since the last fuel oil thread
Quote from: slipperymongoose on June 04, 2013, 02:08:09 AM
You got a beauty here havnt had this much fun since the last fuel oil thread
:) :laugh: ;) :D 8) :thumb: :cheers:
Quote from: sledge on June 03, 2013, 07:34:07 AM
Quote from: peteGS on June 03, 2013, 04:36:18 AM
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.
Shouldn't that be `under`?
Yup! Brain fart right there! Nothing like contradicting one's self in the same sentence... :cookoo:
Some interesting points....Yes GPS does have some limitations and weak points..
Fortunately for me, I don't often go thru tunnels, other than really short ones.....I don't ride in the big city, and the mountains around here are not too tall....
So for me the GPS works wonderfully..........
The only issue I find is that it takes the GPS some time to initially lock on to the satellites....especially if the unit has been shut down for a couple of days.......
I see why GPS is so useful for nautical or aviation as there are no obstructions to the sky....
I can see that a hub sensor, which is calibrated an be extremely accurate...THis is what our MC speedo is....Really the only problem with the GS500 speedo is that the numbers are printed on the dial in the wrong places....
I remember reading old car magazines...they always had a bicycle wheel apparatus bolted to the rear bumper to give accurate road test data..... can be extremely accurate in a wide variety of conditions.........
What about "inertial sensors" this is the big deal in aircraft now...the AHARS..also used in robotics...
You have solid state "gyros" and accelerometers......in a tiny package...
Cookie
Quote from: BrianRC on June 03, 2013, 10:47:25 PM
I would love to add my two cents here as a road rally competitor (in cars) I have seen a huge difference in the various speed measurement instruments available. I drive an older car that uses a mechanical cable driven input from the gearbox and it is fairly accurate..up to 35mph, after that you start to get slippage of the gears (spinning on the input shafts) on the inside of the speedometer. Some are better than others but they all have a deviation.
The international standard regarding how much vehicle speeds can be off was put into effect in the late 80's if I remember correctly (65 on my 1983 car speedo is closer to 70 actual) so I missed out on that by a few years. GPS is accurate speed and distance wise only if you are traveling in a fairly straight line without any quick direction changes (switchbacks anyone? :icon_mrgreen: , those can alter readings by a few 10ths of a mile and momentarily throw speed readings. GPS also suffers from line of sight signal reception issues, if you are in the mountains and there are no satellites directly above, you loose signal accuracy and it starts to guess on your speed and direction based on last known direction and speed; or it cuts out entirely.
I use a purpose made rally computer that reads pulses off the hub of an un-driven wheel of my car and they display speed to a 10th and distance down to the 100th of a mile (or km if you like). It still can be thrown off by wheel slip of course but it is the answer to GPS inaccuracy and can easily be tuned for different wheel and tire sizes.
I think for all intents and purposes a dedicated Gps more than fits the average riders needs.
My Acewell uses a pickup strapped to the left fork leg and a magnetic bolt replacing one of the disc bolts to trigger it, so the resolution is pretty good and it's programmed with the diameter of the front tyre so you can get nice and accurate.
(http://i594.photobucket.com/albums/tt26/starpoint73/GS450/Acewell/IMG_4604.jpg) (http://s594.photobucket.com/user/starpoint73/media/GS450/Acewell/IMG_4604.jpg.html)
I added 10 or 15mm to the diameter when programming it so that it would over read a little.
http://www.speedotuner.com/install.html
Here's somebody's solution....funny though...one of the calibration methods is to use a GPS!
You can use time over distance too...very accurate...
Cookie
Sure........We've been using magnetic pick ups on bicycles for many years....We do a roll-out test to get accurate tire circumference and simply program the unit...
Cookie
Quote from: peteGS on June 04, 2013, 05:10:09 AM
My Acewell uses a pickup strapped to the left fork leg and a magnetic bolt replacing one of the disc bolts to trigger it, so the resolution is pretty good and it's programmed with the diameter of the front tyre so you can get nice and accurate.
(http://i594.photobucket.com/albums/tt26/starpoint73/GS450/Acewell/IMG_4604.jpg) (http://s594.photobucket.com/user/starpoint73/media/GS450/Acewell/IMG_4604.jpg.html)
I added 10 or 15mm to the diameter when programming it so that it would over read a little.
Yup, nothing new to that principal!
I just marked the tyre and floor with some tape and rolled it forward three different times and split the difference for my circumference measurement :thumb:
Easy!
Apparently on the Honda VFR, the speedo is out by 10% but the odo is accurate. Maybe the manufacturers are trying to give us a bit of breathing space in terms of speeding fines :laugh:
Pretty much. Good feature though. Means we keep our licences to figh another day
The GS500 is also pretty accurate on the odo.....I figure 8% off on the speedo ...
I think the philosophy is twofold....
1) to keep the speedo on the conservitive side to prevent speeding tickets
2) the speedo boasts a higher than real speed...so we can boast on how fast we go.....
But let's get real...who's kidding who?
I mean I know there is a 8 to 10% error...so I just go 10% faster
Also when I have the GPS fitted and it give accurate speed...well the speed IS accurate...if I'm over the limit...well, I AM speeding...simple as that........
It's like I know people who set their clocks 10 min fast so they are not late for meetings and stuff....
dooouuuughhhhh!
Cookie
only 10% faster?!! c'mon own up!! ... we wont tell!! :icon_twisted:
Quote from: sledge on June 02, 2013, 11:54:33 PM
Yep......over indicating by about 10%
Don't worry about it, they all do it :thumb:
yep 10% on average.
Those replacement digital displays do almost everything my expensive rally computer does except for being able to adjust and calibrate them on the fly, even the magnetic sensor is pretty much the same (I just use a proximity sensor which is more durable but not quite as sensitive as the magnetic hall-effect sensors)
Twocool, I think I remember hearing about those inertial sensors being used in black box recorders and from a bit of reading the good 'ol wikipedia when integrated with gps an other inputs they can be pretty damn precise. If we could get that in a small handheld gps that would be pretty damn cool!