does GPS calculate real-time speed?
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Senior User
Joined: Sep 2003
Posts: 171
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From: SE Michigan
does GPS calculate real-time speed?
Dont' know much about GPS's... but thought I'd caught on this Forum people comparing their SPEEDOMETRE readings to their GPS's...
- Does a GPS in fact display REAL-TIME speed?
- Is this more accurate than stock Speedo?
- Is visibility of the screen easy enough to read (e.g. could a GPS be used IN LIEU of a speedometre? i.e. in situations where NON-stock tires are used and speedo has NOT been re-calibrated??).
Any suggests for an affordable, simple-to-use GPS would be great!! Might also nice to have for snowmobiling up north this year.
Thanks much!
- Does a GPS in fact display REAL-TIME speed?
- Is this more accurate than stock Speedo?
- Is visibility of the screen easy enough to read (e.g. could a GPS be used IN LIEU of a speedometre? i.e. in situations where NON-stock tires are used and speedo has NOT been re-calibrated??).
Any suggests for an affordable, simple-to-use GPS would be great!! Might also nice to have for snowmobiling up north this year.
Thanks much!
Posting Guru
Joined: Nov 2002
Posts: 1,535
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From: I'm lost somewhere in NJ -- can someone please find me?!?!?!?
1) GPS does display real-time speed. But they are better at calculating ture speed on flat ground than hills.
2) More accurate -- not if your factory speedo is tuned well. Yes if your factory speedo is off. Just get TrueSpeed, get the factory speedo working right, and don't worry about it
3) Screen can be easy to read if you use a mount. But the Speedo location is convenient. Besides, if you're running no-stock tires and the speedo is off, so are your tranny shift points as well as the odometer. The tranny shifts are the bad part, as your truck is not shifting at the right points for optimal power.
Don't try to band-aid it with a GPS. If your speedo is off a considerable amount, get it fixed with a TrueSpeed. I put bigger tires on my truck, and my speedo is off by about 2-3MPH at 60. Doesn't bother me enough to fix, but if it were more, I definately would.
2) More accurate -- not if your factory speedo is tuned well. Yes if your factory speedo is off. Just get TrueSpeed, get the factory speedo working right, and don't worry about it
3) Screen can be easy to read if you use a mount. But the Speedo location is convenient. Besides, if you're running no-stock tires and the speedo is off, so are your tranny shift points as well as the odometer. The tranny shifts are the bad part, as your truck is not shifting at the right points for optimal power.
Don't try to band-aid it with a GPS. If your speedo is off a considerable amount, get it fixed with a TrueSpeed. I put bigger tires on my truck, and my speedo is off by about 2-3MPH at 60. Doesn't bother me enough to fix, but if it were more, I definately would.
Senior User
Joined: Mar 2002
Posts: 132
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From: Castle Rock, Co
Re: does GPS calculate real-time speed?
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- Does a GPS in fact display REAL-TIME speed?
- Is this more accurate than stock Speedo?
- Is visibility of the screen easy enough to read (e.g. could a GPS be used IN LIEU of a speedometre? i.e. in situations where NON-stock tires are used and speedo has NOT been re-calibrated??).
Any suggests for an affordable, simple-to-use GPS would be great!! Might also nice to have for snowmobiling up north this year.
I have had a cheapo backpacking/hunting GPS for 3+ years now and it can display mph. I have used it to check both my vehicles speedos. The trick is to hold your speed steady because there seems to be a delay in showing the current speed. There did not seem to be any significant error in my trucks speedo. You certainly could verify the impact that oversize tires would have to your speedo with a GPS unit but using it on a daily basis would be a PITA. Look up GPS units at a web site like REI or something and stick with the most basic unit (easier to use) that provides what you need. BTW, I always wonder why in dash nav systems are so popular when I think that higher end GPS units will do about the same. Good luck.
- Does a GPS in fact display REAL-TIME speed?
- Is this more accurate than stock Speedo?
- Is visibility of the screen easy enough to read (e.g. could a GPS be used IN LIEU of a speedometre? i.e. in situations where NON-stock tires are used and speedo has NOT been re-calibrated??).
Any suggests for an affordable, simple-to-use GPS would be great!! Might also nice to have for snowmobiling up north this year.
I have had a cheapo backpacking/hunting GPS for 3+ years now and it can display mph. I have used it to check both my vehicles speedos. The trick is to hold your speed steady because there seems to be a delay in showing the current speed. There did not seem to be any significant error in my trucks speedo. You certainly could verify the impact that oversize tires would have to your speedo with a GPS unit but using it on a daily basis would be a PITA. Look up GPS units at a web site like REI or something and stick with the most basic unit (easier to use) that provides what you need. BTW, I always wonder why in dash nav systems are so popular when I think that higher end GPS units will do about the same. Good luck.
Senior User
Joined: May 2003
Posts: 481
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From: St. Petersburg, FL
A GPS will provide incredibly accurate, real-time velocity under certain conditions; Most have been adressed above: 1)Flat ground, 2)straight line.
A gps takes a reading on your position at fractions of a second and based on how much your position changed in a given amount of time, velocity is calculated.
However, if your on an incline or on a turn, the distance you travel is greater than what the GPS can perceive. If your turning on a curve, you are traveling along the circumference of a circle, but the GPS will segment this circle as a series of points; the reading will be off. Same goes for an incline. The GPS perceives your motion as a horizontal distance across the surface of the Earth, but since your changing elevation concurrently, the GPS will once again be off.
On straight and level roads, it will be undoubtedly more accurate.
A gps takes a reading on your position at fractions of a second and based on how much your position changed in a given amount of time, velocity is calculated.
However, if your on an incline or on a turn, the distance you travel is greater than what the GPS can perceive. If your turning on a curve, you are traveling along the circumference of a circle, but the GPS will segment this circle as a series of points; the reading will be off. Same goes for an incline. The GPS perceives your motion as a horizontal distance across the surface of the Earth, but since your changing elevation concurrently, the GPS will once again be off.
On straight and level roads, it will be undoubtedly more accurate.
Senior User
Joined: Mar 2003
Posts: 340
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From: NY
Cheaper units may only utilize 3 to 6 sattelites to get a fix. A higher end unit will utilize 12 sattelites for a fix. I know when I upgraded from a 6 to a 12 on my boat it was a lot quicker in updating the mph.
My Garmin Street PilotIII in my truck slightly lags behind in updating the speed.
Then there is DGPS and WAS, but that is more relavent to boats.
My Garmin Street PilotIII in my truck slightly lags behind in updating the speed.
Then there is DGPS and WAS, but that is more relavent to boats.
Posting Guru
Joined: Feb 2003
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From: Dallas
real-time.. not quite. If you are holding a constant spee then yes, it is very accurate. Any changes in your speed will show on the GPS with a slight delay. This rreally shows if you are doin about 55 then hit the brakes and stop as quick as you can. That will show you th delay.
I will support haroutd 100% in buying a truspeed. You can get it very very accurate and you don't have to keep an eye on your GPS. With a little fine tuning of my truspeed i got it withen one tenth of a mile per hour on my speedo. Very worth it
I will support haroutd 100% in buying a truspeed. You can get it very very accurate and you don't have to keep an eye on your GPS. With a little fine tuning of my truspeed i got it withen one tenth of a mile per hour on my speedo. Very worth it
