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GPS VS Speedometer

Discussion in '2nd Gen. Tacomas (2005-2015)' started by coffeesnob, May 19, 2010.

  1. May 19, 2010 at 5:08 PM
    #1
    coffeesnob

    coffeesnob [OP] Well-Known Member

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    What would you say is the most accurate? A 2010 Tacoma speedometer or a Garmin GPS. My Garmin is consistently reading about 2 MPH faster than my Tacoma speedometer. The odometer is dead nuts with the Garmin but with all the electronic trouble Toyotas are accused of having it makes me wonder which is right. Maybe it has to do with the cruise control. Whats your thoughts, ya I know 2 MPH is not a big deal but it is a brand new truck. Has anyone else checked out the speedometer to see if it is acccurate? Thanks!:confused:
     
  2. May 19, 2010 at 5:09 PM
    #2
    moto932

    moto932 What's the matter, Colonel Sandurz? CHICKEN?

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    i've heard gps is more accurate.
     
  3. May 19, 2010 at 5:09 PM
    #3
    BravesFan

    BravesFan The MOST Badass Offroad Truck

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    all of the speedometers are off just a little bit.....
     
  4. May 19, 2010 at 5:12 PM
    #4
    Brunes

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    The difference between your SPEEDO and your ODO is the display mode. The ODO is displayed from a digital source to a digital display. The SPEEDO is a digital source displayed on an analog display. Digital to Analog creates inherent error, usually on a non linear scale (It'll be like 2% off...so 1mph off @ 50 mph and 2mph off at 100 mph...as an example. 10% is allowable I think...)

    So...your ODO is right, and the GPS gives the correct speed. Your needle is just a little error prone.
     
  5. May 19, 2010 at 5:14 PM
    #5
    coffeesnob

    coffeesnob [OP] Well-Known Member

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    they are?
     
  6. May 19, 2010 at 5:15 PM
    #6
    P-Hill Tacoma

    P-Hill Tacoma Well-Known Member

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    When garmin says 70 my Tacoma says 73-74. Haven't checked the odometer. Just figured it was off the same as the speedometer.
     
  7. May 19, 2010 at 5:18 PM
    #7
    oofy15354

    oofy15354 Proud Tundra *****

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    yes + or - 10% is the amount allowed by law. idk why we cant make ones that are dead on with all of our fancy technology but thats the way it is. slight difference sin tire size will also make a difference.

    just for reference, i found my base 2004 reg cab to be just about spot on
     
  8. May 19, 2010 at 5:20 PM
    #8
    Brunes

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    We can- but producing those needle assemblies to such perfect tolerances would be far more expensive and have another part that could fail and/or require maintenance.

    I think most folks have found scangauge units show speed correctly, as read from the ODBII port.
     
  9. May 19, 2010 at 6:01 PM
    #9
    BuckNakedBooda

    BuckNakedBooda There's no place like 127.0.0.1

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    Both my Garmin 765T and 660 are dead on with the speedometer of my Tacoma from 0 to 80 mph. My Honda Element that I just traded in was always off 2mph when the speedometer went above 20 mph.
     
  10. May 19, 2010 at 6:04 PM
    #10
    zdog

    zdog Well-Known Member

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    This is about where I am....2010 Tacoma 4 cylinder.

    ZDog
     
  11. May 19, 2010 at 6:15 PM
    #11
    crf69

    crf69 scraping my emblems off my plasti-dip

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    ummm yeah
    on my cbr1000rr my bike said 76 garmin zumo550 said 71
     
  12. May 19, 2010 at 6:15 PM
    #12
    crf69

    crf69 scraping my emblems off my plasti-dip

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    ummm yeah
    wait....wrong forum.....too many windsor and seven up's
     
  13. May 19, 2010 at 7:08 PM
    #13
    bruinsrme

    bruinsrme Well-Known Member

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    well GPS could be affected by terrain.
    Is the GPS a 2D or 3D resultant.
    If 2D then it is esentially using Ve and Vn (velocity north and velocity east)
    If a 3D fix is calculated then Vv (velocity vertical) or altitude is figured in to the equation.
    If 2D is used it doesn't account for the up and down of the terrain.
    Another factor is how often a fix or position is calculated. If every 3 to 5 seconds then you loose that data in between fixes. the GPS only calculates point to point (fix to fix) or successive approximation, so if you are going 65mph and go thru a large sweeping turn the GPS may not actually calculate the total distance traveled but only from when you entered the turn to some point in or out of the turn increasing or decreasing the actual distance traveled.
    Angle of elevation of the satellite also is a factor as well as if the satellite(s) have the latest Almanac and Ephemeris data.
    If I was to believe one over the other I would believe both.
    Oh by the way, is your GPS calculating speed using a statute mile 5280 feet or a nautical mile 6000 feet. More than likely its using a nautical mile.

    gps fix.jpg
     
  14. May 19, 2010 at 8:00 PM
    #14
    DarkKnight4684

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    I have the same thing happen to me. I have the Garmin 765T and it is consistently off by 2 MPH. When I used the GPS in my Scion tC, it was dead on. So yes, something is off in our Tacomas.
     
  15. May 20, 2010 at 4:47 AM
    #15
    coffeesnob

    coffeesnob [OP] Well-Known Member

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    I don't know if its 2d 3d or what..it is a Nuvi 260 or 65. I drove 1800 miles the last week and it was consistently off a few MPH. It sounds like the guy with the Scion is having pretty much the same disparity as me. To the posts that say 10% is allowable by law I believe you but I think that is ridiculous that car makers can't get closer than that. In fact I don't ever remember having a speedometer that I didn't really trust, especially brand new.:confused:
     
  16. May 20, 2010 at 4:52 AM
    #16
    Brunes

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    How many have you compared to GPS tho?? My two cars right now are the only ones I've had a GPS in- and most of the time your speedo shows faster than you are really going- so you won't get tickets or anything...
     
  17. May 20, 2010 at 5:20 AM
    #17
    hookedontronics

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    gps for sure. but my nav and speedo match up perfect
     
  18. May 20, 2010 at 5:28 AM
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    n2advnture

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  19. May 20, 2010 at 5:40 AM
    #19
    rjclemen

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    Also, if you have increased your tire size and or your gear ratios that can also change the speedometer. I remember when I lifted my chevy and it went off by 5 mph. Also GPS accuracy will be based upon the signal strength.
     
  20. May 20, 2010 at 7:10 AM
    #20
    05Moose

    05Moose Middle-Aged Member

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    Wow, it's amazing how these topics come up over and over. Not sure on the "base" 2wd tacoma's, but for the rest of us it's been shown over and over that the odo is accurate and the speedo reads 6% fast. So if you're speedo says 65, you're doing 61. That's one of the main reasons people switch to a 265/75 from a 265/70 tire...because it eliminates the speedo error and makes it accurate.

    BTW, among those that have tested it with GPS, I haven't. I've discovered my error when following another vehicle that was dead-accurate. And since then have tested it against the radar checks. 6% error is accurate. Reads 3 mph fast at 40, 4 mph fast at 65, etc.
     
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