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Thread: Accuracy on GPS

  1. #1

    Talking Accuracy on GPS

    I have been wondering how accurate a Garmen quest GPS is on the MPH. I have a 2005 RXP stock (except a prop) that always seems to be faster then an average RXP, I average 68.9 mps on an average day and have reached 72.8 more then once.

    9' above sea level.
    85-95 degrees Panama city Beach Florida.

    I was able to pull with ease away from a ultra 250 but the ultra was still in the break in period.

    When I bought my ski it was one of a pair of RXP's that I bought at the same time that were 60 days old. So there was no way that it had been modified.

    Has any one else had this kind of speed out of a stock RXP? Or should I try another GPS?
    Last edited by jetskidj; 09-19-2007 at 01:42 PM.


  2. #2
    jaycee's Avatar
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    A GPS is normally pretty damn accurate, most I have heard two of them be off by is .3-.4 mph btwn brands. When you use it, check to see if your are in 3D GPS mode or 2D.... there should be a box in one of the screens that shows your "accuracy." Optimal would probably fall btwn 15-20 ft but I won't settle the GPS into it's holster until it is at least below 25ft. It should pick up more sat's as I go and it get's "warmed up."

    I know there is another reason that for some reason it "surges" and this causes false high's but I haven't ever had it happen to me, but someone will chime in with it.


    A stock boat really shouldn't be doing 72.... so what kind of prop????

    68.9 is very possible if everything is perfect!!!

  3. #3
    Scotty's Avatar
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    I think they all do that. Some people have said something about them spiking when cornering. I have a Garmin 76C. This past Sunday I watched it more than I usaully do. It consistantly stayed at 72.4 to 72.6 but when I came back to the ramp at the house it had a max speed of 73.2. I don't know when it jumped to 73.2 but it must have been just for a second. I reset all the numbers before I left the ramp.

    Scott

  4. #4
    the prop was a stock repitched.

    The 72mph must just be a spike error. I will look for the 3d option.

    Thank you for your help.

  5. #5
    My new toys at work bruinsrme's Avatar
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    it depends on the type of GPS system
    Just a handheld is accurate within 15 meters (more like 6 meters)
    Most GPS units can track up to 12 satellites. The real problem is if the calulation is based on satellites to hi or lo on the horizon the quality of the position fix is impacted. good elevations would be 20 to 65 degrees off the horizion. but most systems will use all obtained satellites.
    far more accurate than Loran or navsat ever was.

    Now if you add DGPS (differential GPS) now you are talking down to a consistent 2 meters.

    Military crypto GPS is extremely accurate (classified)

  6. #6
    Moderator RX951's Avatar
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    for 3 years, I've compared my Garmin Forerunner 201 to the Stalker Gun at Mudbug, and I'm off .1 every year vs the Stalker. sometimes high sometimes low. but only .1 off. (tenth)
    and I'm usually locked in well with 5-7 satellites at any given moment.
    with Garmin's software they need a minimum of 3 to locate

  7. #7
    My new toys at work bruinsrme's Avatar
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    Quote Originally Posted by RX951 View Post
    for 3 years, I've compared my Garmin Forerunner 201 to the Stalker Gun at Mudbug, and I'm off .1 every year vs the Stalker. sometimes high sometimes low. but only .1 off. (tenth)
    and I'm usually locked in well with 5-7 satellites at any given moment.
    with Garmin's software they need a minimum of 3 to locate
    3 satellites to obtain lat long and speed. (2 dimensional fix)

    4 or more satellites to obtain lat, long, altitude, velocity east, velocity north, velocity vertical and velocity total (3 dimensional fix)

  8. #8
    cheatin' piston popper addicted's Avatar
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    Is the unit mounted firmly, or bouncing around in the glove box? If its in the glove box, that's your problem. if it's hard mounted, maybe borrow a buddies unit to compare?

  9. #9
    Moderator RX951's Avatar
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    cool, I learned something new bruin

  10. #10
    It is hard mounted.

    Its just still not possible for a stock RXP to hit that high of a speed.

    I did loss my gps a couple of months a ago but a replaced with the same model. It had the same result. I need to try a differnet model.

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