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I borrowed a gps from a friend. Looks like my speedo is off by about 6% roughly. If I ride 80 I'm showing about 75 on the gps. That is simply nice to know. Passing a couple speed traps last weekend had me wondering. Now I know.
It would be interesting to mount a gps on the bike, but unless I'm heading for big city traffic, it's pretty much a luxury. I like all the features though. Cool stuff.
 

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If you spend more time with the GPS, you will find that the error varies.

On my bike sometimes I'm 5 mph off, and sometimes they agree.

Most people assume the GPS to be the most accurate, and that is probably true, but it has errors too. But most likely the speedo on your bike isn't consistant.

If you really like the GPS, rethink your position on luxury. There are used ones out there that are pretty cheap.

I love having mine, and I am on my 3rd upgrade.

Street Pilot

Street Pilot 3

Street Pilot 2610.



When I got my first one, it really set me free. There are a lot of people out there that say that you can never be lost when you have a full tank of gas. I never had that much confidence. I always stuck to roads that I know. But once I got the GPS I really felt free.

I warned my wife once that there were two accessories that I couldn't be without:

#1 the GPS

#2 the CB.

The warning part was because if my GPS broke, I would buy a replacement right away. And we really can't afford it.;)
 

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I work with GPS regularly in my work at the Satellite, Positioning, and Inertial Navigation (SPIN) Laboratory at OSU...

Be careful about using the GPS...while a kinematic solution is possible, algorithms vary widely and the solutions can vary depending on a number of factors (to numerous to list here). In particular, ALL GPS units do not generally handle acceleration well; given a straight stretch of road and constant velocity will give the "best" solution. They certainly won't get close to the accuracy of laser ranging...so I wouldn't try to use GPS challenge to challenge a ticket in court!
 

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That's interesting that the gps would be off day by day. I wonder what would be the cause of that? The accuracy of those things is facinating, at least in relation to location. An engineer friend of mine sets up a remote link site and then runs a super accurate gps, to within 1 or 2 cm I believe he said. I think it would be nice to have a nice color waterproof gps mounted on the bike. I've been exploring those with touch screens and numbers big enough for a gloved finger.
Here in ND, you really don't get lost on a highway unless a real heavy fog rolls in. I did lose my sense of direction while deer hunting one fall when a deep fog came in. I had to walk until I found a fence and then follow that until I found a section road. Then I had to follow the road around the section until I found my truck. Wow. I was exhausted. A gps would have bee great right then, but that was before they were common.
Now, when I take my planned bike trips out of state, I'm definately gonna want a nice gps to leave bread crumbs when I get of the main roads.
 

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I didn't think 1 or 2cm was possible due to their inbreed inaccuracies unless your engineer friend has a military unit and signal access.
 

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clouddragon9 wrote:
I work with GPS regularly in my work at the Satellite, Positioning, and Inertial Navigation (SPIN) Laboratory at OSU...

Be careful about using the GPS...while a kinematic solution is possible, algorithms vary widely and the solutions can vary depending on a number of factors (to numerous to list here). In particular, ALL GPS units do not generally handle acceleration well; given a straight stretch of road and constant velocity will give the "best" solution. They certainly won't get close to the accuracy of laser ranging...so I wouldn't try to use GPS challenge to challenge a ticket in court!
That is intriguing. I wonder, brand for brand, quality for quality, if there are any speed accuracy ratings for a gps module? I see the screen on this one I borrowed has an accuracy estimate for location, but not speed.
 

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Clouddragon, in my searches so far, gps discussions tend to give a decent gps a speed accuracy of .5 mph.
Bear in mind I'm a nube to gps so I'm not arguing against your knowledge, just surprised that they would not be more accurate.
In my modest testing today on my ride, the gps response lagged behind a second or so, and fluctuated possibly a half mile per hour, but otherwise held on very cosistantly.
 

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I have a Magellan in my Truck .. It is spot on with the Speedo. although I didn't try to fool it changing speeds.. Now I love to get lost. and not worry a bit. It always takes me home. Sometime in a weird sorta way. Tiger Direct has Re manufactured ones for $99. Garman and Magellan..
 

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I found that I need a good stretch of road where I can set the cruse in order for the GPS to catch up. Once it does, it seems to be dead on with the speedo.

And I also have been able to take a road I would normally pass by. And then take another road I've never seen. When it's getting late in the day, I touch the "Go Home" button. I'm getting to know my way around better now.;)

One more note,,,,,,,,,,,, when I took my trip out west, I had to pass through several large cities. I hate city driving, and the GPS put me through them all with ease. I was able to be in the correct lane at all times. If the route split, I was ready for it.
 

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I have the SP 2610 that was mentioned by Wolfman. It showed in the GPS info that it was accurate to 7ft (with 7 satellites looking at it) when we went to the top of Mt. Magazine in Arkansas on Saturday. It shows how many satellites are looking at you at that moment, accuracy, elevation (I was curious about elevation and found the rest). Its a neat GPS for the money. I still see them refurb'd for around 160-180. I'll buy another one if this one falls by the wayside. I've had my refurb for about 3 years now.
 

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I also have a Garmin 2730 and a Garmin Nuvi 350.

The 2730 has never been wrong, and has been extremely accurate with speed indication. It and my way old Garmin Street Pilot III track each other flawlessly.

Not that damn Nuvi. It gets lost, has to be rebooted. It lags behind my vehicle at least 2 seconds and I have missed lane changes in St. Louis with the Nuvi. That did it for me. I turned it off, and finished that trip with my older 2730.

The Nuvi's database for business addresses is also flawed. It consistantly wants to route me in the weirdest manner to get to an address. The 2730 makes much better routing decisions.

I really wish there were a way to figure out that stuff before the dollars leave my hand.

I suppose that there are forums for GPS stuff too. Just never looked for one.
 

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AZgl1500 wrote:
I really wish there were a way to figure out that stuff before the dollars leave my hand.

I suppose that there are forums for GPS stuff too. Just never looked for one.
This site is for Garmin owners, a good bunch of guys there. Its where I got the info before purchasing my SP.
 

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I use a Garmin Nuvi (the discontinued 350) and love it for the most part. GPS is now so reasonable that I would not consider it a luxury these days. For example, here is a refurbished Tom Tom for only about $50! http://www.newegg.com/Product/Product.aspx?Item=N82E16858194072

I found that the GPS and my speedo were about 3mph off. Speedo showed me going faster than the GPS did. I did notice a little lag with the refreshes with my Nuvi , but I also noticed that one of the newer models that a family member has seems to refresh/process a little faster. Like anything, those of us who buy the technology when it is new and expensive are just guinea pigs for those who wait a little bit. I think now is your time!
 

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I still don't use or have one at all, does that mean I'm over the hill :(



I still use my navigator (the boss):Dshe is dead on no matter what
 

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Continuously Operating Reference Stations (CORS) locations are often utilized as "substitute" GPS fixes and possess millimeter accuracy. Given enough time and the right operating conditions, most high end GPS receivers (the kind used for surveying, etc) can easily achieve cm accuracy. Military receivers utilize a second signal with shorter bit length to achieve higher accuracy, since the time of travel (satellite to earth) can be determined more accurately. Their signal is encrypted for obvious reasons.

The biggest issue to GPS positioning is the ionosphere - the solar wind causes the ionosphere to become charged, which alters the timing of the GPS signal path. Most GPS algorithms incorporate a standard ionospheric model to "correct" for this issue, but if the iono starts to deviate from the model, more error will insue. As we start to enter the 11 year sun spot cycle, more extensive solar storms = a wild(er) iono = degraded GPS. In some instances, the iono storms can become so large as to temporarily block the GPS signal. GPS will generally worse around 12-3 pm, and much better at midnight for this reason as well.

Other big problems are multi-path, where the signal bounces off things like buildings or trees before finally arriving at your receiver (lengthening the time of arrival), and the geometry of the satellites relative to your position - better to have them widely spread out than clustered together. Again, various algorithms have different ways of mitigating these isses, with varying results. In general, any decent receiver should locate you within 10 meters or less; in most cases, within 3 meters.

GPS is sampling at a rate of ~1 reading per second and determing position at point A and then at point B. The time of the two readings is also determined based upon an oscillating crystal. Velocity is therefore simple distance / time. The accuracy depends upon the quality of both the time estimate and the position estimate. If you are going straight at constant velocity, the average of many readings becomes pretty good. If you just drive around in a circle, the accuracy will be less. At stong accelerations/ decellerations the "action" is happening faster than the 1 second sampling rate and the unit will have trouble getting a good estimate. A decent GPS unit should give a pretty close result to the speedometer and give an indication that one (or the other) is WAY off, but I wouldn't utilize it to calibrate a speedometer or challenge a ticket! (Although with a good lawyer anything is possible :-/ )
 

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About the speedo: My wing's speedo reads, unlike most, slower than actual speed, according to any of my GPS's.

Additionally, during the restoration of the Ascot, I took apart 2 speedos to make 1. The Ascot's, anyway, are not direct driven but use a magnetic wheel spinning inside a steel cup to make the needle sweep. This seems to me to be able to introduce quite a bit of error, especially if the magnet is not spaced properly inside the cup.

On a GPS note: I took mine with me on a flight to Houston several years ago. It was cool monitoring position, altitude, and speed.
 

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I would not travel without my GPS. I went to Texas last month and did not get lost or have to ask for directions one time. When I am riding near home, I can ride around all day and get totally lost; hit the home button and home I am headed. My wife and I have explores all over Maryland, West VA and VA, looking for antique malls and never missed a single one.

My daughter's bought us a Tom Tom, One 3rd addition (refurbished) for around $100.00.

The only disadvantage is, it is not waterproof.
 

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I don't have a GPS on my Wing but on the weekend tested my car speedomoter against the GPS and it was bang on. We had a car full and I was in the back seat and the wife was driving and I told her I was watching her speed on the GPS. Didn't seem to bother her. :D
 

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What are you all using for a mount for the gps? I have a BlackBerry Tour and am looking at getting a gps for the bike. I also wanted to find a mount that could accomodate both the BlackBerry and GPS, but am clueless. As for GPS, I'm looking at a Garmin model, but not sure which one yet. Hoping to save some money some where and buy something soon.
 

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