Lean Angle: Why is the number so hard to find?

Thank you for using the EatSleepRIDE Motorcycles App. Some of you have tried the Ride Record feature. Some of you have even looked at the data! And a small few have even emailed me to ask why their motorcycle sometimes displays wonky in the ride data visualization, even without a crash…

For this, I say, 'here's why...'

When we started to build the ESR App, measuring the lean angle looked like a reasonably simple and trivial feature to build in. It's not.

While CrashLight is a very complex feature, detecting the angle of lean of a rider on a motorcycle is equally difficult to teach a smartphone to master.

I'll try to explain.

Which angle are you measuring?

First we must determine the angle we're measuring. You'd think this would be an easy answer, right? And if you don't do maths, it is. However, to collect lean angle to the degree we need, we must measure the angle as the deviation that is perpendicular to your plane of travel. Positive is the deviation to the right, and negative is the deviation to the left. Dead simple right? Well…

Perhaps a few images will help.

Hopefully, the images above explain more obviously how the ESR App measures lean angle. Yes, it would be simple to find the lean angle if we could guarantee the phone was always affixed directly to the motorcycle. Why? Because it's the smartphone device that contains the sensors, not the motorcycle.

So, let's consider the iPhone for a minute. The sensors measure the orientation of the phone in space. So far, so good right? (It's why they do a decent job of enabling you to play Super Monkey Ball.)

To accurately detect the lean angle, the ESR App must set a fixed direction and measure the angle from that static point.

Now, imagine that the smartphone is also capable of moving. Once moved, either in your pocket or top box, the fixed direction is no longer fixed.

Oh, and the rider is moving too. Forward, backward, side to side. Even the most sedate rider will move in the saddle from time to time.

And now imagine that you only want to measure the angle relative to the plane of travel. All of a sudden, there's another set of variables to deal with.

To recap then, we're using the smartphone (which moves) to measure the angle of the rider (who moves) on a motorcycle (which moves). To manage all the 'movement' we designed the lean angle to calibrate when you start moving at speed.

I tried to draw the concept in a diagram but my head hurt too much. In other words, it's a very tough problem involving so much maths, we had to find an engineering grad student to figure it out.

How can I record the most accurate lean angles?

With every release, we're adding improvements to a number of features including lean angle.

In the upcoming release 1.2.5, lean angle is again improved. In traffic with frequent stops, you may see a wonky angle when your speed is at zero. Once you pick up speed, your lean angles will be accurate to +/- 3%!

Here's a few pointers that will help improve your lean angle accuracy:

• The most reliable lean angle calculations will be collected with your device affixed to the motorcycle, either on the bars or in a tank bag
• If CrashLight is enabled, carry your smartphone snugly in a jacket pocket to prevent it from moving around; in the event of a crash the smartphone should be on you, not the bike
• Don't carry the smartphone in a pants pocket or a pannier/top box as it can move around in there
• In all cases, try to ensure the phone moves as little as possible

Lean angle may not be perfect yet, but we're dedicating to improving the accuracy with every release. Please help us improve the feature by sending feedback on what you're seeing.

Ride on.