Month: August 2022

Power Biking – Smartphone App Measures Cyclist’s Power

Chuck

If you are interested in power biking and have a smartphone, you may be interested in observing your power output measured in watts. Smartphones typically have sensors that can be used to measure acceleration. Most smartphones also have a GPS receiver to determine your location and speed. Add some weather information and you have the makings of a power biking app.

Power Biking App Accuracy For This Ride

The best accuracy for this ride is highlighted in bold.

SensorsCrank Power Meter (Watts avg.)Cykelstrom (Watts avg.)Difference (Watts)Margin of Error (Watts)
External Speed and Cadence141.84142.380.53+/- 1.44
GPS Speed and External Cadence141.84139.71– 2.13+/- 1.62
External Speed Only142.96152.959.99+/- 1.67
GPS Speed Only142.96149.166.21+/- 1.41
Table created using Bland-Altman Analysis using a 4iiii Precision Pro dual sided crank power meter as the standard with 95% confidence level.

Discussion Of This Ride’s Results

This ride’s most accurate results are when external speed and external cadence sensors are used in conjunction with sensors internal to the smartphone. The smartphone used for this test ride was a Motorola G6 which has the Bosch BMI160 inertial measurement unit or IMU. I purchased this smartphone as a refurbished unit for around fifty dollars. The external cadence and speed sensors were purchased as a pair for around sixty dollars, however, you can find these sensors for a lot less. The cost of a typical power meter is easily five to ten times more expensive. The accuracy of a crank based power meter can be as good as +/- 1%, however, for me I am happy with accuracies +/- 10% and I like being able to move my smartphone to many different bikes.

The following graph is a power distribution that compares the biking power meter app, Cykelstrom, to a dual sided crank based power meter.

Power distribution comparison of Cykelstrom using and external speed and cadence sensor to a 4iiii Precision Pro dual sided crank power meter.

For an example of power distributions when riding a mountain bike please read Mountain Biking Hartman Creek State Park.

For a more detailed discussion of the power biking app and comparison to a crank power meter please read Power Distribution Comparison: Cykelstrom Bicycle Power Meter App vs. Crank Power Meter.

Strava Activity

Click on the map to visit this activity in Strava. Feel free to follow all of our test rides of the power biking app.

Elapsed Time Moving Time Distance Average Speed Max Speed Elevation Gain Calories Burned
01:42:42
hours
01:38:50
hours
25.38
mi.
15.41
mph
24.66
mph
448.16
ft.
1,037
kcal
Yesterday I felt the universe was conspiring against me by creating obstacles to prevent me from riding, i.e. flat tire, battery too low in the power meter, finally ready to ride and it starts raining…. So I listened and I didn't ride. Today, the universe was with me as it felt like I was riding a gravitational wave through the country. Never felt better or stronger. My app data was within .53 watts of the power meter +/- 1.4 watts. Pretty looking distribution curves and everything. Lesson learned: It pays to listen when the universe is speaking to you.

Follow Cykelstrom Test Rides On Strava

The Cykelstrom Power Biking App Is Only Available On Google Play

bicycle power meter app download button
Cykelstrom Bicycle Power Meter App Download
cykelstrom scan QR code
Scan to go to Cykelstrom on Google Play

Bike Power Meters – Mountain Bike On Rural Road Using The Cykelstrom App

Chuck

These are the results of a short test ride using the Cykelstrom Bicycle/Bike Power Meter App compared to a crank type power meter.

Mountain Bike Power Meter App Accuracy For This Ride

SensorsCrank Power Meter (Watts avg.)Cykelstrom (Watts avg.)Difference (Watts)Margin of Error (Watts)
External Speed and Cadence100.5494.38– 6.17+/- 2.95
GPS Speed and External Cadence100.5489.71– 10.83+/- 2.91
External Speed Only101.69100.18– 1.51+/- 3.20
GPS Speed Only101.6994.94– 6.75+/- 3.15
Table created using Bland-Altman Analysis using a 4iiii Precision Pro single sided crank power meter as the standard with 95% confidence level.

Discussion of This Ride’s Results

We decided to do a short ride after dinner as we were both recovering from the Wausau 24Hr Endurance Mountain Bike Race from the previous weekend. Using Cykelstrom during that race taught me a few things about my racing. To see the video and read about the race please visit Cykelstrom Mountain Bike Power Meter App Test Ride – Wausau 24.

Back to this ride’s results, we can see that out of all of the combinations of using external sensor to not using any external sensors that the worst case scenario is within 14% of the standard power meter for this ride. The best case scenario was within 5% of the standard power meter. The surface of the road was fairly smooth. The mountain bike used was a Trek Top Fuel 8 with the suspension locked. With the suspension locked there was still some movement of the suspension so it was not like riding a hard tail or road bike. I believe the results of this ride reflect the moving suspension.

Strava Activity

Click on the map to visit this activity in Strava. Feel free to follow all of our test rides of the Cykelstrom Bike Power Meter App.

Elapsed Time Moving Time Distance Average Speed Max Speed Elevation Gain Calories Burned
00:20:23
hours
00:19:45
hours
4.45
mi.
13.53
mph
18.02
mph
58.73
ft.
135
kcal
Stacey wanted to go for a short ride after dinner. It was 90+ degrees Fahrenheit today and humid, but when the sun went behind the clouds it was pleasant to be riding

Follow Cykelstrom Test Rides On Strava

The Cykelstrom Bike/Bicycle Power Meter App Is Only Available On Google Play

bicycle power meter app download button
Cykelstrom Bicycle Power Meter App Download
cykelstrom scan QR code
Scan to go to Cykelstrom on Google Play

Cykelstrom Mountain Bike Power Meter App Test Ride – Wausau 24

Chuck

With the Cykelstrom mountain bike power meter app revision 1.30 completed and tested on the local single track, it was time to give our app a test at the Wausau 24 endurance mountain biking race. I captured video of the first lap and included results for the first two laps of the race.

Video of the first lap of the Wausau 24 Endurance Mountain Bike Race

Mountain Bike Power Meter App Accuracy For Lap One

SensorsCrank Power Meter (Watts avg.)Cykelstrom (Watts avg.)Difference (Watts)Margin of Error (Watts)
External Speed and Cadence116.7123.87.1+/- 3.6
GPS Speed and External Cadence116.7101.5– 15.2+/- 3.4
External Speed Only119.2146.727.5+/- 4.2
GPS Speed Only119.2119.70.5+/- 3.9
Table created using Bland-Altman Analysis using a 4iiii Precision Pro single sided crank power meter as the standard with 95% confidence level.

Mountain Bike Power Meter App Accuracy For Lap Two

SensorsCrank Power Meter (Watts avg.)Cykelstrom (Watts avg.)Difference (Watts)Margin of Error (Watts)
External Speed and Cadence121.3141.520.2+/- 3.5
GPS Speed and External Cadence121.3109.1– 12.2+/- 3.3
External Speed Only122.8164.441.6+/- 4.0
GPS Speed Only122.8128.05.1+/- 3.8
Table created using Bland-Altman Analysis using a 4iiii Precision Pro single sided crank power meter as the standard with 95% confidence level.

Discussion Of This Ride’s Results

This test ride of Cykelstrom, demonstrates the challenges estimating power when riding in extreme conditions, like a heavy canopy.

During the ride, GPS reception was poor as indicated by the heading information using the magnetometer instead of GPS most of the time. Cykelstrom looks at the accuracy of the GPS heading information and will switch to the magnetometer if accuracy is low. It appears that since GPS accuracy was low, then other GPS derived data was not updated frequently enough to give good power estimates. For this reason, I recommend users of the Cykelstrom App use an external speed sensor and cadence sensor when GPS signals are unreliable. To learn how to add external Bluetooth sensors to Cykelstrom please visit Adding Bluetooth Sensors to Cykelstrom.

When using an external speed and cadence sensor, accuracy was greatly improved for this ride. The Cykelstrom mountain bike power meter app was within 6% at best and 17% at worst, on average, when compared to the standard crank power meter.

As the developer of Cykelstrom, I ride every opportunity possible to improve the app. Your suggestions and feedback are welcome at developer@cykelstrom.com.

Strava Activity

Click on the map to visit this activity in Strava. Feel free to follow all of our test rides of the Cykelstrom Bike Power Meter App. This is lap one of the Wausau 24 Race.

Elapsed Time Moving Time Distance Average Speed Max Speed Elevation Gain Calories Burned
01:30:13
hours
01:29:20
hours
10.82
mi.
7.27
mph
17.81
mph
682.74
ft.
894
kcal
First lap, started slow, caught back of pack in bottle necks anyway.

Follow Cykelstrom Test Rides On Strava

The Cykelstrom Bike/Bicycle Power Meter App Is Only Available On Google Play

bicycle power meter app download button
Cykelstrom Bicycle Power Meter App Download
cykelstrom scan QR code
Scan to go to Cykelstrom on Google Play

Road Bike Power Meter – Test Ride West of Oshkosh, Wisconsin

Chuck

Road bike power meter app test ride for Cykelstrom version 1.30 which is available to the public on the Google Play Store. Version 1.30 changes the app displayed averages at the end of the ride for moving time only. To make better use of the limited resources on some smartphones, improvements were made to GPS data collection threads and fine tuning of the power estimate calculations.

Road Bike Power Meter App Accuracy For This Ride

The best accuracy for this ride is highlighted in bold.

SensorsCrank Power Meter (Watts avg.)Cykelstrom (Watts avg.)Difference (Watts)Margin of Error (Watts)
External Speed and Cadence148.18154.706.53+/- 1.47
GPS Speed and External Cadence148.18150.462.28+/- 1.44
External Speed Only149.20162.6213.42+/- 1.63
GPS Speed Only149.20157.978.77+/- 1.66
Table created using Bland-Altman Analysis using a 4iiii Precision Pro dual sided crank power meter as the standard with 95% confidence level.

Discussion Of This Ride’s Results

This test ride of Cykelstrom, tests the accuracy of version 1.30. This version was created to improve the performance of the app on smartphones which are more limited in computing resources.

Highlighted in bold, the table shows that when using the GPS with an external cadence sensor presents results which are closest to the crank power meter. To learn how to set up a cadence sensor in Cykelstrom please visit Adding Bluetooth Sensors to Cykelstrom.

We continue to improve Cykelstrom to enhance your ride experience. If you have a question or comment please reach out to me at: developer@cykelstrom.com.

Kind regards, Chuck

Strava Activity

Click on the map to visit this activity in Strava. Feel free to follow all of our test rides of the road bike power meter app.

Elapsed Time Moving Time Distance Average Speed Max Speed Elevation Gain Calories Burned
01:36:09
hours
01:35:00
hours
25.27
mi.
15.96
mph
23.37
mph
438.32
ft.
1,040
kcal
I made some updates to the power calculation algorithm, in addition I made the averages displayed at the end of the ride to represent only moving time. If you take a long water break, your down time is not represented in the averages.

Follow Cykelstrom Test Rides On Strava

The Cykelstrom Road Bike Power Meter App Is Only Available On Google Play

bicycle power meter app download button
Cykelstrom Bicycle Power Meter App Download
cykelstrom scan QR code
Scan to go to Cykelstrom on Google Play