Forum home Road cycling forum Road general

Byton gps concern

andy 3654andy 3654 Posts: 183
edited January 2014 in Road general
I have the Bryton 50 gps computer but for a while I have noticed that sometimes it is a little optimistic.
For example I know I am not an overly fast rider but when I look at the top speed at the end of my ride I am surprised to see it say that I have gone at nearly 30mph. I could believe it if I was going down hills but most of my route is flat with very minor bumps not even hills.
Another thing which leads me to disbelieve it is when I turn it on at home as the altitude always changes.

So my main question is, is this just limited to Byton models or is this a common thing among any gps unit?

Cheers for any help.


  • This is common among all GPS units. Some are quite good at dealing with altitude and low signal, but some struggle, especially in cloud cover.
  • rolf_frolf_f Posts: 16,015
    It helps if you set the elevation of your starting point as the barometer is determining altitude change based on the known variation.

    When you upload the files, the unit can see what the elevation is meant to be based on the digital elevation map so it will calibrate the recorded data to that.

    I've recently started using a Bryton 20 without a barometer and once you upload the data, the calculated elevation change is pretty similar to the corrected recorded elevation data. Really, the barometer only makes a worthwhile difference if you want to make use of its data during the actual ride.
    Faster than a tent.......
  • crakercraker Posts: 1,739
    What they said ^

    A GPS captures position. To calculate speed it takes the difference in two position readings and divides it by time. However any inaccuracy in your position measurement will have a drastic affect on the speed calculated for that segment, whilst the distance inaccuracy will quickly even out. So, no GPS is not a reliable gauge of speed. Get a speed sensor (can you? I have one for my Garmin) if it's important.
Sign In or Register to comment.