Garmin 201 accuracy experiment

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  • kevinpratt823
    Fast Electric Addict!
    • Aug 2012
    • 1361

    #1

    Garmin 201 accuracy experiment

    We were talking on another thread about gps, so I had this idea to run just as an experiment. I have (3) Garmin Forerunner 201's, so I took them all for a ride. It was rush hour, and I was on my way home from an errand. The readings in the photos are all consecutive, without resetting. It was slow backroads, onto a congested highway, which finally opened up gradually just enough to get a couple spurts just over the last reading. The units were on my dashboard and I couldn't see the readout, so I watched the spedometer and when I topped out over the previous reading I was abruptly in traffic again at the next exit, that's when I pulled them down and took the pic. The readings were right on point with what I was seeing on my spedometer (2013 Nissan Frontier), and for each of the readings, my max speed was not held for more than a second or so, otherwise I would have rear ended somebody.

    I was coming to my exit when I had an opening that I thought I could break 80mph(it's a 55mph speed limit), but I noticed the SUV a ways behind me had a peculiar ammount of antennas on it
    I slowed and changed lanes toward my exit and watched the unmarked state police vehicle cruise right by

    The end result was that the greatest difference between the 3 units was .1mph, and it was not always on the same unit, it varied. I would like to do this again and watch them all to see if the numbers change approx the same, as I have no doubt it takes a certain ammount of time for a speed to register accurately, this is why I only really trust passes where I actually hold it wide open for a few seconds at least.

    I am not claiming that this proves anything or whatever, or looking to spark any debate, just wanted to share the results an interesting experiment, you can draw your own conclusions if you desire.
    20150519_151515_resized.jpg20150519_151612_resized.jpg20150519_152318_resized.jpg20150519_152837_resized.jpg20150519_153044_resized.jpg
    Last edited by kevinpratt823; 05-19-2015, 04:58 PM.
    My private off road rc track
    https://www.youtube.com/watch?v=XC3H...yaNZNA&index=8
  • kevinpratt823
    Fast Electric Addict!
    • Aug 2012
    • 1361

    #2
    the rest.....
    20150519_153127_resized.jpg20150519_153237_resized.jpg20150519_153601_resized.jpg
    My private off road rc track
    https://www.youtube.com/watch?v=XC3H...yaNZNA&index=8

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    • kfxguy
      Fast Electric Addict!
      • Oct 2013
      • 8746

      #3
      I did the same thing with two of them. They both always had the same reading. Then I had my son hold one and watched it while I went to certain speeds in my car and I'd call out the speed and he'd verify. There was no distinguishable variance
      32" carbon rivercat single 4s 102mph, 27” mini Rivercat 92mph, kbb34 91mph, jessej micro cat(too fast) was

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      • iridebikes247
        Fast Electric Addict!
        • Dec 2011
        • 1449

        #4
        They're accurate man. I went to Florida on vacation a month ago and sent texts to a few forum members of my gps reading 535 mph lol. The plane had an option to view the altitude, speed, etc and my gps was spot on the whole way.
        Youtube: https://www.youtube.com/channel/UCSr...6EH3l3zT6mWHsw

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        • Luck as a Constant
          Make Total Destroy
          • Mar 2014
          • 1952

          #5
          Yeah looks like those are super accurate.
          No question about that.
          I almost bought one, but then I realized I barely run my boat anyways so what's the point lol


          Sent from my iPhone using Tapatalk
          There's a hole at the center of earth where the rest of the world sinks but i stand still...

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          • kevinpratt823
            Fast Electric Addict!
            • Aug 2012
            • 1361

            #6
            Originally posted by Luck as a Constant
            Yeah looks like those are super accurate.
            No question about that.
            I almost bought one, but then I realized I barely run my boat anyways so what's the point lol


            Sent from my iPhone using Tapatalk
            EBay man, if you watch, wait, and bid you can easily score one for under $50.
            And about that "barely running your boat" thing..........ya we need to work on that one lol.
            My private off road rc track
            https://www.youtube.com/watch?v=XC3H...yaNZNA&index=8

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            • Luck as a Constant
              Make Total Destroy
              • Mar 2014
              • 1952

              #7
              Yeah dude, honestly I've been really into mtb lately.
              Any nice days I ride instead of going to the lake.
              Thought putting a new boat together would spark me up, but I'm just kinda meh about it.
              I just haven't been finding the time or interest much.
              I ran once last week


              Sent from my iPhone using Tapatalk
              There's a hole at the center of earth where the rest of the world sinks but i stand still...

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              • JimClark
                Fast Electric Addict!
                • Apr 2007
                • 5907

                #8
                It proves they are consistant

                Sent from my SGH-M919 using Tapatalk
                "Our society strives to avoid any possibility of offending anyone except God.
                Billy Graham

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                • kevinpratt823
                  Fast Electric Addict!
                  • Aug 2012
                  • 1361

                  #9
                  Originally posted by JimClark
                  It proves they are consistant

                  Sent from my SGH-M919 using Tapatalk
                  Yes, consistent with each other as well as my truck's speedometer, which I would imagine has to be accurate within certain tolerances in order for production of a vehicle to be legally approved.
                  My private off road rc track
                  https://www.youtube.com/watch?v=XC3H...yaNZNA&index=8

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                  • Spartanator
                    Fast Electric Addict!
                    • Oct 2013
                    • 1060

                    #10
                    Hmm, imagine that. They are accurate! Lol
                    Point well proven!
                    Why are you bothering me? I want to see your boat!
                    32" CF Rivercat--- built by "kfxguy" (SOLD)

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                    • kevinpratt823
                      Fast Electric Addict!
                      • Aug 2012
                      • 1361

                      #11
                      Just an update- 2 units in the boat, one on top, one inside under a FG/kevlar hatch on 7s, bot read exactly the same, 94.3mph. I intended to make a few runs, but the pond claimed the one on top on the next run/crash.
                      My private off road rc track
                      https://www.youtube.com/watch?v=XC3H...yaNZNA&index=8

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                      • kevinpratt823
                        Fast Electric Addict!
                        • Aug 2012
                        • 1361

                        #12
                        Originally posted by kevinpratt823
                        Just an update- 2 units in the boat, one on top, one inside under a FG/kevlar hatch on 7s, bot read exactly the same, 94.3mph. I intended to make a few runs, but the pond claimed the one on top on the next run/crash.


                        Sent from my SM-G920V using Tapatalk
                        My private off road rc track
                        https://www.youtube.com/watch?v=XC3H...yaNZNA&index=8

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                        • T.S.Davis
                          Fast Electric Addict!
                          • Oct 2009
                          • 6221

                          #13
                          GPS us data points and time to figure out the speed. The trouble is that the data points have a fudge factor themselves. The longer distance you can run the more accurate they are. More points to use I n the math. 3 side by side in a car should be dead nuts. If you're running them in boats use as much pond as you can.

                          An old SAW guy that passed away a couple years ago used to call them GPGuess. The accuracy on the data point gathering was less than stellar back then.
                          Noisy person

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                          • kevinpratt823
                            Fast Electric Addict!
                            • Aug 2012
                            • 1361

                            #14
                            Based on the fact that virtually every time I pick my boat off the platform and carry it 8' to the water it registers +/- 2mph almost instantly, yes, I would say the accuracy has come a long way. But for me to be confident in readings I want to at least see (gradual)acceleration to full speed, plus held there wide open for 3 seconds. This last pic was a total of 8 passes I think on 7s, with a total distance of 1.38 miles, so each full pass would be over 1/8 mile. 100mph for 3 seconds works out to .083 miles covered, or 439'. That's a reasonable number of data points if the device can register a 3-4' motion I would think.

                            Sent from my SM-G920V using Tapatalk
                            My private off road rc track
                            https://www.youtube.com/watch?v=XC3H...yaNZNA&index=8

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