Cycling apps calculate distance mainly from GPS, by adding up the distance between recorded positions. Some can also use a wheel sensor, which measures wheel rotations and multiplies by wheel circumference. Speed comes from distance over time.
GPS method
The phone records position about once per second. The app filters noise and adds the segments. This works with no extra equipment.
Wheel sensor method
A sensor on the wheel counts rotations. Distance equals rotations times wheel circumference, so setting the correct circumference matters. It works where GPS does not, such as indoors on a trainer with a sensor.
Speed
Speed is distance divided by time. GPS speed is smoothed because instantaneous readings are noisy. Average speed depends on whether stops are counted.
Moving time versus elapsed time
Elapsed time includes stops. Moving time does not, so average speed using moving time is higher.
Why numbers differ between apps and bike computers
- Different filtering.
- Wheel circumference settings.
- Different treatment of stops.
Wheel circumference explained
If you use a wheel sensor, the computer must know how far the wheel travels in one rotation. This depends on the tyre size and pressure. Many sensors use a table value for each tyre size, and some riders measure by rolling the wheel one turn on the floor. A small error in circumference becomes a small, consistent error in distance.
Choosing which method to trust
- Outdoors with a clear sky, either method works.
- In tunnels or on trainers, a sensor works and GPS does not.
- If the two disagree by a lot, check the wheel setting first.
How stops change the numbers
A ride with many traffic lights has a lower average speed if stops are counted. If your app pauses automatically, the average rises. For comparisons, use whichever method you used last time.
Where HALEBIT fits
HALEBIT calculates ride distance from your phone’s location while Bike mode is running, and shows it live next to time and elevation. Weekly totals appear in History, and you can set a weekly distance goal in Settings.
See the cycling tracker page or explore HALEBIT →
Keep reading
- GPS cycling tracker explained
- What data should a cycling tracker record?
- How to track a bike ride on Android
Quick questions
Is GPS or a wheel sensor more accurate?
A correctly calibrated wheel sensor can be very consistent. GPS needs no setup and is accurate outdoors.
Why is average speed different on my bike computer?
It may use moving time, while your app uses elapsed time, or the reverse.