GPS are amazing tools to improve your ride, but like finding a  construction detour on your ride home there are many things that can interfere with their data. Trees, buildings or other structures can cause interference and even your lycra jersey if the unit’s signal is weak enough.

Bridges can be especially devious as your GPS may read that you’re below the bridge, adding a significant amount of imaginary elevation gain and loss on a flat section of a ride.

In this example, I went downtown, entered a large office building and went up 13 flights of stairs. The GPS track went crazy. These trackpoints were calculated by my smartphone and recorded by the app.
bad-gps-tall-building
In this example, my GPS track accuracy was affected by the constant cover of tall trees over the trail and hilly terrain. It looks like I took two parallel trails when it was actually the same trail both ways.
bad-gps-trail-example

How do I improve my GPS accuracy?
It doesn’t matter if you are using a handheld device like a Garmin, Magellan, or a smartphone, all GPs receivers will be affected by these building and terrain situations. Your device’s most accurate times is when the device has a clear view of the sky on open terrain.

  • Keep your device on the handlebars
  • Stay away from large metal structures like tall buildings, tunnels, and power lines.
  • If you must keep it in a pocket or backpack, get your device as close to the top or surface as possible
  • Keep other electronics away from your device. Keeping your smartphone right next to the GPS might cause some drift.
  • Use a different case, some cases with magnetic clasps or metal shielding will interfere.

Happy trails!

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