Woo vs Xensr

[CaliRider]

I heard that the woo should soon be compatible with apple watch

$250 (woo) plus apple watch $350 = $600.

$0 Xenser app plus apple watch $350 = $350.

[maffhieu]

I found this review of the Xensr Session app for the Apple watch :


Customer Reviews
I want it to work, I swear!

by ChugItNugget
Some information seems to work (speed, time, distance) sometimes it doesn’t (3 hour session I paddled 265,000m? I doubt it) and never once has it transferred to my phone. Even after the latest update that “fixed” that issue it still has yet to sync (and those sessions are lost, no tracking other than a short overview in activity). Upside it does time track waves so easy to check Surfline camera at that time then getting a rough guess. Doesn’t really track waves under 3’ though. I want to like this more, like a lot more. Group of coworkers have the app and want to get more metrics, specifically area surfed but at this point, open water swim may just be the answer. Would revise review if the app was fixed.


https://itunes.apple.com/us/app/xensr-s ... 76251?mt=8


I know he used the app for surfing but if it doesn't work for surf how well can it perform for Kitesurf...


IMO it seems too good to be true ... but maybe one day

[Largorn]

From my understanding, the Xensr Apple Watch app works with the GPS of the watch.
I think that GPS is not accurate enough for jump height measurement. The US government says that GPS accuracy of smartphones is typically around 5m:

For example, GPS-enabled smartphones are typically accurate to within a 4.9 m (16 ft.) radius under open sky

https://www.gps.gov/systems/gps/performance/accuracy/
This is the error that results from the device, given a perfect GPS signal. The signal itself also has a slight deviation

On May 11, 2016, the global average user range error (URE) was ≤0.715 m (2.3 ft.), 95% of the time.

https://www.gps.gov/systems/gps/performance/accuracy/

Wikipedia says (without a source) that the accuracy is about 5m horizontally (https://en.wikipedia.org/wiki/Error_ana ... m#Overview). I did not find information about vertical accuracy. Maybe that's even worse, as it is typically not that important for civilian purposes.
Also, as we all know from GPS navigation, smartphones (and watches) do not permanently calculate the position from GPS, only every 1 or 2 seconds. While no big problem for navigation, this would be really bad for jump height, as you only stay on the highest point of the jump for a split-second. I would be really surprised if the app could alter the delay the watch makes between different GPS fixes. Even if it could, the battery life would probably drop extremely.

GPS seems kind of the obvious way to go. If it would have worked properly I would have expected WOO (and also Xensr with the Air) to go down this route in the first place and not try to develop a way more complicated system that relies on heuristics to estimate jump heights from accelerometers.

I have an Apple Watch 2 and downloaded the Xensr App yesterday, waiting for wind now to be able to try it. I also have a WOO 2, so I will make a comparison session.
Did anyone have a go with it yet? I would be really surprised if it works properly, but it would be a pleasant surprise .

[davedej]

Interesting for a first proper data comparisson...!
We did some on the Tom Tom watch, which turned out that this watch on GPS cannot be used within meters.

Dave
We Test Kites

[Xensr]

From my understanding, the Xensr Apple Watch app works with the GPS of the watch.

Great post! You are spot on about GPS and why GPS doesn't work for jump heights. Which is why all of the kitesurfing sensors use inertial sensors to provide a jump height value.

[Largorn]

From my understanding, the Xensr Apple Watch app works with the GPS of the watch.

Great post! You are spot on about GPS and why GPS doesn't work for jump heights. Which is why all of the kitesurfing sensors use inertial sensors to provide a jump height value.

Thanks for the response. But doesn‘t that mean that the jump height feature of your Sessions app is broken by design? Or does it use inertial sensors instead of GPS? If yes, how do you differentiate arm / body movement from movements that are actually connected with the jump? I thought that this is the reason why the sensors are placed on the boards, not the body.

[Xensr]

Thanks for the response. But doesn‘t that mean that the jump height feature of your Sessions app is broken by design? Or does it use inertial sensors instead of GPS? If yes, how do you differentiate arm / body movement from movements that are actually connected with the jump? I thought that this is the reason why the sensors are placed on the boards, not the body.

Meaning that we don't use GPS for jump height calculation. Sorry for not being clear on the earlier reply.

[Nicko]

which strap are you guys using on your apple watch in the water?

[deniska]

I heard that the woo should soon be compatible with apple watch

$250 (woo) plus apple watch $350 = $600.

$0 Xenser app plus apple watch $350 = $350.

Good luck measuring your jumps with the watch alone.
The only way to do it is to throw it down at the apex of your jump and count seconds before it hits water