Apple applies for patent to calculate cyclists' power from wind resistance and other factors

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RobertFrith
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Re: Apple applies for patent to calculate cyclists' power from wind resistance and other factors

Postby RobertFrith » Thu May 18, 2017 11:47 pm

It's an interesting challenge, something anyone who uses Strava must contemplate from time to time as they hack their way around their local riverloop.

Wind speeds and directions for specific areas are perhaps the low hanging fruit in realising the dream of deriving power output from a gps track. Road surface is mentioned, but have they talked to Jan Heine? You'll need to know about tyre width if you're going to get into road surface. And bicycle+rider weight? The differences in drivetrain efficiency between a '92 Tommasini (my daily driver) and a contemporary roadie are significant. They also need to consider whether you are riding solo or in a bunch, and, if in a bunch when you're at the front and when you're being sucked along.

Strava's best guesses of power output are correctly ignored. The technology noted in the patent is a reasonable attempt to improve it.

The one obvious way to improve this data would be the ability to compare performance with riders who are using power meters. Apple already uses this sort of technology to refine positioning of lost or stolen devices; the IP of a device gives a rough location, wifi signals from nearby Apple mobile devices are used to refine the position. The more Apple mobile devices your lost or stolen device sees, the better the definition of it's location.

Imagine you're in a bunch with someone who has a power meter, or you pass through an area just before or after a power meter user. That data connected with your weight and speed would up the quality of an estimated power output heaps.
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Re: Apple applies for patent to calculate cyclists' power from wind resistance and other factors

Postby Alex Simmons/RST » Fri May 19, 2017 8:08 am

RobertFrith wrote:It's an interesting challenge, something anyone who uses Strava must contemplate from time to time as they hack their way around their local riverloop.

Wind speeds and directions for specific areas are perhaps the low hanging fruit in realising the dream of deriving power output from a gps track. Road surface is mentioned, but have they talked to Jan Heine? You'll need to know about tyre width if you're going to get into road surface. And bicycle+rider weight? The differences in drivetrain efficiency between a '92 Tommasini (my daily driver) and a contemporary roadie are significant. They also need to consider whether you are riding solo or in a bunch, and, if in a bunch when you're at the front and when you're being sucked along.

Strava's best guesses of power output are correctly ignored. The technology noted in the patent is a reasonable attempt to improve it.

The one obvious way to improve this data would be the ability to compare performance with riders who are using power meters. Apple already uses this sort of technology to refine positioning of lost or stolen devices; the IP of a device gives a rough location, wifi signals from nearby Apple mobile devices are used to refine the position. The more Apple mobile devices your lost or stolen device sees, the better the definition of it's location.

Imagine you're in a bunch with someone who has a power meter, or you pass through an area just before or after a power meter user. That data connected with your weight and speed would up the quality of an estimated power output heaps.

Your optimism in the ability of such a device to come anywhere near to accurately providing power output is, well, unjustified. It'll be not a lot more than a light comic relief random number generator.

Using your power meter using ride buddy as a guide is completely useless - the power demand for two riders riding next to each other not only is quite variable rider to rider (e.g. for one of my mates his power riding next to me on flat road is ~35% less than mine), not to mention the simple act of riding next to someone actually changes the power required compared with riding by yourself at the same velocity (because of the complexity of aerodynamics - the pressure differential on each rider is affected by the location of the other rider - I've even tested it experimentally and it's not insignificant).

Another example, there is a ~10% difference in power required to ride along a flat road at 30km/h between a head and tailwind of just 1km/h (a wind speed rated calm, low enough that we cannot even feel it when standing still and anemometers cannot register it).

The various energy demand factors are just too complex and are highly variable, especially aerodynamics (which represents over 75% of the energy demand for most rides/riders). That's why we have devices already which directly measure the forces and velocities applied to relevant bicycle components (e.g. pedals, cranks, spiders, hubs). These have been shown, when good models are used correctly, to be reliable, accurate and precise.

Devices that attempted to measure the energy demand components and estimate power from that are not new nor novel, ibike have done this for a long time. Measurement of air movement and resulting pressure differentials however is very complex.

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RobertFrith
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Re: Apple applies for patent to calculate cyclists' power from wind resistance and other factors

Postby RobertFrith » Fri May 19, 2017 11:03 am

You're right, the variables involved are many and and the interactions so complex that it's likely that measuring power directly will remain the only accurate method forever. My point is just that deriving an estimated power from speed and weight alone is so wildly inaccurate that any attempt to improve it will likely yield big gains.
Using your power meter using ride buddy as a guide is completely useless - the power demand for two riders riding next to each other not only is quite variable rider to rider (e.g. for one of my mates his power riding next to me on flat road is ~35% less than mine)

Presumably you can account for the difference? If you can account for it then it's entirely conceivable that a system can as well. Whether any system can improve accuracy enough to compete with power meters is another matter :-)
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Re: Apple applies for patent to calculate cyclists' power from wind resistance and other factors

Postby Alex Simmons/RST » Fri May 19, 2017 3:17 pm

RobertFrith wrote:Presumably you can account for the difference? If you can account for it then it's entirely conceivable that a system can as well. Whether any system can improve accuracy enough to compete with power meters is another matter :-)

No, you can't. Unless you think a wristwatch has the ability to know the precise air movement, what you are wearing, your position on the bike and CdA data for each bit of clothing and kit set up and position and yaw angle, as well as know the relative location of everyone and everything in proximity to impact airflow, then I very much doubt it. The level of imprecision in such an approach is greater than the normal seasonal variation in human performance (power) for an experienced regular rider. IOW it's pretty pointless aside from the gimmick factor that might motivate some people to move more than they do now (but the exercise industry is littered with unused devices).

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Re: Apple applies for patent to calculate cyclists' power from wind resistance and other factors

Postby Comedian » Sun May 21, 2017 9:41 am

I reckon this is a pretty interesting development by Apple. I reckon it could lead to athletes monitoring blood sugar while training.. :shock:

https://www.macrumors.com/2017/05/18/tim-cook-testing-apple-watch-glucose-monitor/

It also clearly has weight loss potential.

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