I am losing confidence in gps

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  • Speed2
    Member
    • Jun 2023
    • 48

    #1

    I am losing confidence in gps



    In the above video, I have it titled 71mph pursuit. I titled it 71 mph because my GPS does read 2 mph slower than what the speedometer in my real vehicle shows. So if my vehicle show 62 mph my GPS will show 60mph.

    Having said that the GPS really said 69mph. The reason I say I loosing confidence in the GPS because I see many people posting gps number on video and to me I wondering what kind of gps the have. I see videos of man posting all kind of 91 mph and all I thinking they boat is not faster than mine.

    I spend sometime studying video footage and distance in the footage. Example when you fully zoom in on a video the distance looks closer to the actual distance as you would see it when looking with your bare eyes. With no zoom it looks twice as far.

    Having said that if you watch my video you will realize it's a big body of water. I does study the video timer and distance that the boat cover over like a 2 second or 3 second span of time.

    What I would like to draw the readers attention to is when the video start begin at 9 seconds to when it just reach 11 seconds.

    Within that 2 seconds span 9 seconds to 11 seconds you can see at 9 seconds the boat is approaching the area where it would appear directly 0 degrees in front the camera. So it like at 45 degrees angle away from the camera to the right. This is the beginning of 9 seconds.

    At the beginning of 11 seconds, just 2 seconds later it like the boat has almost vanished, it has become come like a dot. This is a boat that read 69 mph on gps. So if 69mph on my GPS looks like that, imagine what 90 or 110mph would look like on my GPS.

    I dare anyone to do this to any of them video where person posting 90 mph and 100 mph on gps. In fact do it for the saw events video too.

    Because if they GPS is right mine is way off.
  • AndyKunz
    Fast Electric Addict!
    • Sep 2008
    • 1443

    #2
    I use GPS a lot. The speedo in both my vehicles is 1-2 MPH off at 70MPH. I have to set my cruise on 71.5 to have a real 70. Going by the GPS speed in my phone, which often is the same as the radars they put in speed zones, so I'm pretty sure the GPS in my phone is accurate.

    When we were developing the GPS devices for the Spektrum radios, we co-flew phones with GPS tracking enabled and the test GPS. They were always very close together (within .1MPH). I trust the GPS.

    GPS does have a time lag, and it doesn't do well with high-speed turns. To make sure your GPS is recording accurately, take the boat down to one end of the course and give it a few seconds of still there. Then drive onto the course, and hold a straight line, then overrun the course at the other end. If your transmitter provides logging features, use that with a telemetry GPS to capture the entire run. If it doesn't, then upgrade to a Spektrum! (I work for Spektrum).

    Andy
    Spektrum Development Team

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    • lohring
      Senior Member
      • Jun 2011
      • 200

      #3
      We did a lot of testing with a radar gun and an onboard Eagletree GPS. The early units had a lag compared to the radar peak speed in our acceleration test runs. Later units were better. We ran GPS units in our record setting full size electric hydro. It was interesting to compare the average speed through the 1 kilometer course versus the gps speed variation as the boat accelerated and/or when Mike lifted. We did similar comparisons during our various Legg Lake SAW runs. The new gps units seemed accurate and give valuable insight.

      Lohring Miller

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      • fweasel
        master of some
        • Jul 2016
        • 4340

        #4
        I trust an $80 gps unit more than the speedometer in my car.
        Vac-U-Tug Jr (13mph)

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        • Speed2
          Member
          • Jun 2023
          • 48

          #5


          This is another video, the gps actually said 61mph. The distance on a pass is around 500 feet. This is the Leopard 4092 2080kv on 4s. If you watch the timer you will notice it's covering that distance is a short space of time.

          Comment

          • Notoriousone
            Member
            • Oct 2022
            • 69

            #6
            Sometimes GPS readings are off due to weather conditions or other factors, I have had very reliable, accurate GPS units give a crazy number every now and then. I think very cloudy or overcast days is when the satellites reception is mostly affected

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