Thinking of starting a new project...

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Re: Thinking of starting a new project...

Postby Max_501 » Thu Feb 14, 2019 8:30 am

Keep in mind that to be useful for teaching/learning you need feedback that directly relates to the input (movements).
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Re: Thinking of starting a new project...

Postby noobSkier » Thu Feb 14, 2019 12:55 pm

This is a good point Max_501. So if we can brainstorm at little bit...seeing as most peoples SMIM is tipping, we could infer tipping quality from angles of the skis relative to each other at various points in the arc...most importantly at the transition when inside ski tipping should lead. I suspect that at higher speeds and forces this becomes less useful as I don't think the sensor is all that sensitive. Forces in the arc would then only be useful for proficient skiers who know as a verifiable fact that their tipping is strong.

CA can also be inferred with a belt around the hips with two sensors on either side. Im not sure how you would measure actual pelvic rotation relative to the femurs, but at least you would know if the hips are level or not. Assuming the skier's tipping is strong it could potentially be inferred from the angle of the skis in addition to the belt sensor array.

Force sensors between bindings and boot would still likely be necessary to infer arc beginning and end. Looking at angles could also work at a lesser degree of accuracy I would think.

Single axis gyro sensor would do the job...not sure if that exists.
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Re: Thinking of starting a new project...

Postby HeluvaSkier » Thu Feb 14, 2019 1:34 pm

What is wrong with video? What is the goal here? Quantify differences between high level skiers across a number of measures? Without a known benchmark, the data will be largely largely useless (this isn't simply a more is better situation, so continuous improvement of a measure doesn't hold up). The data could quantify what an experienced coach with a good eye would be able to qualify... But I don't see that it would ever be superior to video.

It might make for a fun apres-ski bar conversation though... "Oh, your averaged max tipping angle on that run was 63 degrees? That's cool... mine was 71 degrees... and I made 35 turns... you said you made 25 turns right?" :lol:

Now... a superior, cheaper and secure (e.g. can't be stolen) version of the SoloShot camera that is smart enough to recognize multiple users from a long way away and know which one to film when, would be of WAY more interest to me.
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Re: Thinking of starting a new project...

Postby noobSkier » Thu Feb 14, 2019 1:43 pm

100% helluva, no-one is a bigger fan of video than I! Any such system should be used in addition to video and experienced coaches. I could see the benefit of a system that could verifiably and objectively tell you that you are initiating with the inside ski for example. The goal is to get objectivity, rather than apres-ski banter.
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Re: Thinking of starting a new project...

Postby HeluvaSkier » Thu Feb 14, 2019 1:47 pm

noobSkier wrote:The goal is to get objectivity, rather than apres-ski banter.


Ever been in a race course? :mrgreen:
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Re: Thinking of starting a new project...

Postby noobSkier » Thu Feb 14, 2019 1:58 pm

God no! Too risky to start at my age! You will find me on the greens, blues and sometimes black runs :D
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Re: Thinking of starting a new project...

Postby ErikCO » Thu Feb 14, 2019 6:28 pm

I think this is one of those things, you have to decide that it sounds like a fun hardware project, get the hardware working, then see what you can do with the data. Especially if it were properly synced to video, it's hard to predict what other insights it might (or might not) give. Also, remember that most of us don't have our own personal videographer! :P
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Re: Thinking of starting a new project...

Postby noobSkier » Thu Feb 14, 2019 8:25 pm

Sounds like a fun summer project with carvers :D
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Re: Thinking of starting a new project...

Postby bmoose21 » Fri Feb 15, 2019 5:55 pm

HeluvaSkier wrote:What is wrong with video? What is the goal here?

Video doesn't give real time feedback, it has to be analyzed after the fact so it can be inefficient. You have to have some way to take video; it can be difficult to take on your own. Video quality is not always great. Video can't see through your boots (although maybe some HSS coaches can!) Video offers clues to ski forces/weighting/balance but can be misleading at times, misinterpreted or unclear for all kinds of reasons.

That said these devices would just augment, not replace video unless they included enough sensing to be able to create an accurate 3D render, or included wearable self-video capability. However I think initially Noobskier's ideas are right on, there are a just a few things that can be tricky self-observe on hill that might not be too difficult to monitor -- one example being CA and the timing of CA.

For me an obvious use of this device would be as as a real-time coaching aid that can provide additional cues that are difficult to otherwise observe while you are on the hill without a coach. My son and I sometimes use a system where we both have radios with earpieces. I can watch him closely while he executes a PMTS drill or skis a few turns... even when he is training slalom. Having MA'd his videos hundreds of times and after watching countless turns I have started to know what to look for -- so in real time I can give him feedback and he can make adjustments that can result in an amazing rate of improvement that we never experienced early on, using only video. He now gets pretty frustrated if he has to spend a session on the snow alone, even if he can get video because he knows he might take an entire day to make a correction that could have been made in one run (or less) if someone were around to observe and provide feedback.
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Re: Thinking of starting a new project...

Postby HighAngles » Fri Feb 15, 2019 7:26 pm

This technology and devices already exist in the golf world. Tiny devices that can be mounted on the club that provide huge amounts of data and recreate the swing in 3D. I have one that's fairly accurate due to the calibration process they use to ensure the device best "understands" where the club is in space.

I could see someone taking this exact same technology and putting one on each boot and maybe your waist. They don't use pressure based force sensors, but instead accelerometers and space positioning. The technology is very good at providing feedback on angles, acceleration, movement distances, etc.

But like Heluva said, it's all kind of useless data in isolation unless you have known "good skiing" threshold values to compare against. Of course these could be collected. My SkyPro for golf includes these threshold values and uses them in training modes that help you focus on one particular aspect of your swing and then you can "groove" train that aspect until you're getting it right. I really see this as being quite possible for ski training.

Go grab some of the developers from the SkyPro unit and get them going on a similar device for ski training... ;)
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Re: Thinking of starting a new project...

Postby noobSkier » Sat Feb 16, 2019 6:20 am

HighAngles wrote:But like Heluva said, it's all kind of useless data in isolation unless you have known "good skiing" threshold values to compare against


I don't know if this is necessarily the case, for instance we know inside ski tipping should lead...can be inferred from angles, likewise BTE dominance can be inferred from angles. Even for the more experienced...like does one ever stop working on tipping? Also, I don't know if I want to see heluva's numbers...I'd probably quit skiing.
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Re: Thinking of starting a new project...

Postby ErikCO » Sat Feb 16, 2019 9:31 am

noobSkier wrote:
HighAngles wrote:But like Heluva said, it's all kind of useless data in isolation unless you have known "good skiing" threshold values to compare against


I don't know if this is necessarily the case, for instance we know inside ski tipping should lead...can be inferred from angles, likewise BTE dominance can be inferred from angles. Even for the more experienced...like does one ever stop working on tipping? Also, I don't know if I want to see heluva's numbers...I'd probably quit skiing.


Inside ski tipping should lead, but by how much? What is a "good" timing, how many degrees does it lead by? And in what situations (different degrees of brushed carve vs edge locked)? At what point do the angles develop, what is their rate of change, when does foot pullback occur and to what degree? And how does foot pullback correspond to different types of turns? These and many other questions are going to be hard to answer without controls. Unless you and Harald can work out a theoretically "perfect" physics model to compare too, there are so many variables that are going to be hard to account for without known controls.

As for Heluva's numbers, we know that they are more than 45 degrees and, on occasion (as shown in videos in another thread) do exceed 90 degrees! I think I'll try to avoid that last part (though I wasn't very successful last week when I mis-timed my flexing in the bumps)! :P
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Re: Thinking of starting a new project...

Postby oggy » Sat Feb 16, 2019 10:53 am

HeluvaSkier wrote:What is wrong with video? What is the goal here?


In addition to the lack of real-time feedback that someone else mentioned, you also got to have someone who knows how to interpret the video...
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Re: Thinking of starting a new project...

Postby noobSkier » Sat Feb 16, 2019 11:21 am

Good points ErikCO, but I suspect that timing, degree of inside tipping, ect. would greatly vary due to variables independent of skill; body type, alignment, speed ect.. This is of course at the sensor level of resolution. We would have to test quite a few skiers to find the commonalities or average ranges. This is probably the way to go. I've been prototyping it on paper...I believe its possible to stay under 100usd per system. Been reading up on various accelerometers...there are some units that offer measurements of angular velocity; this might make force sensors unnecessary.
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Re: Thinking of starting a new project...

Postby tangem1 » Mon Mar 04, 2019 12:01 pm

My daughter has been using Carv for 2 seasons now and while the instruction it gives doesn't match up with PMTS and it does require the insert in the boot it has been a very useful tool. Specifically it has a beta feature that allows you to shoot video with another iphone or ipad that has the carv app installed and then at the end of the day or after the run you can sync the video shot with the other phone that recorded the run and then you can play the video and it overlays every single metric the carv recorded on the video. You can see the fore aft balance, inside/outside pressure, edge angle, etc frame to frame. Maybe the hardware is easy to build but if someone wanted to build something that uses PMTS methodology instead of the PSIA like they did it might be easier to see if CARV would allow plugins to be built for the existing carv app, ie a PMTS instructor and drills instead of PSIA instructor and drills. I do agree thought that another sensor to pickup counteracting and counterbalance would be necessary to try to translate the tool to PMTS effectively.
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