Water ski GPS data acquisition

[Horton]

If we did have GPS data on a skis path in relation to the balls, pitch, roll, speed and such would it really tell us anything useful?  I mean it would be very cool but would it be a training tool? Would it be worth money? I am not saying that I have an idea . . . .  but as you guys know I am always thinking.

 

Note to DW . . . . that thing we talked about today was the key. Keep it under your hat and I will show you what I found.

 

 

[DW]

Drivers thought data acquisition when in it's infancy was ridiculous, now it is standard on every race car, used for car, engine and driver analysis.  It could not only tell a lot about the ski but be a great training tool for skiers and ultimately ski schools.  In engineer speak, data is king.

[Horton]

Ok so lets say that we had it today. What exactly does it tell us about out skiing? How does it help me learn to ski better?  

Let assume that we have:

Path in relation to the balls (GSP)

Speed (GPS)

Accelerometer data (from an accelerometer, duh)

Pitch and roll - 6 axis (Not sure how but I think this is critical) 

DW suggests position of the handle and other data feeds. Add position of head and or CG. Well that is a way cool idea but is far from the capability I am looking at. As of today lets table these ideas as future but out of the scope of this discussion.  

[DW]

I think once you start to look at and analyze ski path data, you will really open up a minefield of information about not only yourself, but also if you expand and do comparative analysis with other skiers.  This data will also tell you a lot about different skis and then as you get more detailed should tell you how a fin change works out, curing an area of concern or lack of optimum performance.

[Horton]

OK DW keep selling me on the idea. I am thinking that I might have found a semi- cheap solution but $500 is not really cheap.

[JCH]

This would be an excellent tool for ski evaluation. Instead of a skier's perception of speed or position in the course, you could have a map with speeds. A ski that is perceived as slow out of the ball, but still early for the next could be actually explained with data that it holds speed better through the turn.

[Horton]

I am thinking more about a general training tool. A one off tool to see how fast a ski is would be cost too much but a tool that helps me ski better is worth a lot.

[lkb]

As far as my skiing goes, I suspect that entering the course with more speeed equals a better pass for me. I would like to be able to verify that with speed data from the gate and throughout the pass. If that proved to be true, I would like to see how much different that path is compared to a slower later pass. So, I would be happy just to have speed and path data. It would just be nice to see if perception is reality.

 

Doesn't somebody make something to strap in a race car that tracks speed around a road racing circuit and also the line that the car ran? Seems like that would be out there somewhere.

[DaveD]

Position and speed feedback would be huge when learning gates at a shorter length.  I wasted a lot of passes this year trying to get around 1 ball without the rope laying in the water. 

[Horton]

The race car suff is out there but it is heavy and $

[DW]

There are several race car systems out there and the range in cost is quite dramatic, basically entry level at $500 up to F1 standards of $40,000 per car commercially (5 times that for unique systems (Ferrari / McLaren)).  I don't think the data acquisition part is going to be the difficulty, it is determining the correct application, waterproofing and knowing what we really want to see / read.  That usually takes some trial and error.  I think we can find a light minimal channel system that will get us what we are looking for.  I think once this gets going the expansion and next steps will really become interesting.

[Horton]

I do need to talk to Kent. Do you know if he has his deal worked out? I was thinking of handing what I had found to him an letting hm have it. I know he was working on live data and not recording from the skier. I am going to record from a box on the ski and then upload to a PC at the dock or at home.

[KG]

What about monitoring rope tension in relation to position in the course also?  For me i seem to ski better when I load the rope less, or at least that is my perception.....

KG

[Horton]

Yea but you are taking next level. I am working with a company that MAY give us off the shelf parts and pieces for GPS and 6 axis. I see a lot of value in things like rope tension but one step at a time. Hell the dream app is includes foot pressure hip angle . . . . . .

[DW]

Strain gauge the line would give the rope tension, probably the second or third step in this process, right after JTH's hip angle measurement.  That one should be soooo simple!

[Old MS Accout]

I like the whole concept but not being an smart enough to use the data, I have no use for it. I would like to know the truth behind the Speed thing. Some skis feel fast and some skis feel fast and stable. It would be great to get to the bottom of that.    

[DW]

Don't underestimate your ability to use the data.  A simple overlay of two runs will allow you to easily see what makes one run better than another or more specifically what section either improves or hurts any particular pass.

[Horton]

Don't over estimate MS

[Old MS Accout]

Kent from the waterski forum site has a program called Lisa and it needs a bit of work. When I had it on, I skied so fast the GPS couldnt keep up with me and we would loose data. But it would be great if you could look back at your pass and compare that to what you felt.  

The roots of this are out there but there needs to be some time and money spent.

[DW]

That is why I was thinking of using an accelerometer, it will keep up and have good fidelity.  Add the GPS element for positioning.  Might be able to input the balls as targets.

[Horton]

That is exactly what I am thinking. In a perfect world the GPS data would be dead on but I am hoping that between the two inputs the data will be pretty good. We will get about 10 GPS points from one ball to the next. Without the accelerometer data I do not think it would be enough. We will see in the spring.

[roda]

Sounds like something I would want on occasion but not all the time.  How about a rental unit?  Would be valuable for schools as they would  become well versed at analyzing and explaining the data.  A library of advanced skiers data to compare yourself to would be useful.  Don't forget head position sensor and device to tell where your eyes are focused.

-Rod A.

[disland]

A tool that you describe along with video tool (like dartfish, I have it) and a lap top computer could be an incredible vehicle for analysis. The key to slalom and for that matter jump is efficiency. What the skier needs to learn is what are they doing from pass to pass to lose their line. In snow ski racing they talk about it constantly, "finding the fastest line". With such a tool a skier could map his best pass when he is skiing his best PB ect and then be able to compare it to his day to day training and see where the loss of effciency is. We have all learned from JB and the WCS crowd that there are different ways to be efficient. Using this tool could enable skiers to improve faster than ever before.

 

I would really like to get involved helping with this project

 

email me at disland@airvana.com

 

dave Island

[DW]

Dartfish is a really good tool, but it does require a separate operator to assist.  We use it frequently in my line of work and it does help out.  I got an interesting lead on some data aq. stuff at a recent trade show, more to come on that when we get something to share.

[Horton]

If you think about what we really need . . . I am not sure the GPS is necessarily that great of a tool.  With accelerometer data only I assume we can easily ID the entry gate wake crossing and each wake crossing from there on. With time we have position down the lake at wake crossings. With 6 channels of accelerometer data we should be able to get speed (rate of change) and direction plus ski attitude.  

 

If this is true what else does GPS give us? Is this crazy talk? DW? Is Butterfield out there??? I know there are a number of engineers who read the forum.

[DW]

John,

Correct, we do not need GPS to get what we are looking for.  Given the fact that the course is a fixed set of points (balls and gates) the ski path will pretty easily define close to where the balls are.  We would be basically superimposing the course on the path data.  The GPS does make that step much easier and potentially more accurate.  You would also not necessarily know which direction in the course the data represents w/o GPS signal or some substitute.

[Horton]

So lets assume that cost is not an issue and that the data quality is good. If the data allowed you to see clear changes in speed and direction could you use it to modify your skiing?

 

I envision seeing differences in terms of acceleration and deceleration from one side of the course to the other. I can also imagine seeing the difference between 1 ball and 3 ball. In seem to carry the handle better in to 6 then into 2 and 4. Length of pull and then speed management from the second wake to the ball.

 

The bad news is that  I think it can be done for $300 but I think the right way to do it costs $600. At that price I am not nearly as interested unless I really thought it would be a meaningful training aid.

[DW]

Before we had it, everybody thought data acquisition would not be that valuable in racing, now there is not a single team that can live without it.  Much of what you end up using is not what you expect going in.  I agree, that this application is very cost sensitive and that is a critical element.

[Horton]

I am torn. I am afraid of chasing the COOL thing and spending a ton of money. I am sure that if someone got it really right it would be helpfull.

[Horton]

Late last year I found these 3 possible off the shelf data acquisition units. I was thinking that I could do the leg work and try to develop a new CBR product. I have since come to my senses.  So for all of you to see, here is what I was looking at.

Cheap but only 3G and maybe a toy at best.

http://www.microdaq.com/occ/pendant/pendant_g_data_logger.php#features

Designed for RC hobby but could easily be applied to skiing

http://www.eagletreesystems.com/

Top Dollar but maybe the best choice.

http://www.sensr.com/gp1.html

[Horton]

Hey DW

How about this? Price is right and I think I gives what we want.

http://www.microdaq.com/msr/index.php

http://www.msr.ch/media/pdf/MSR145-manual-E.pdf

 

[DW]

I'll scope it out.

[roda]

Is anyone an IEEE member that can get the full text of this article?

 http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?tp=&arnumber=1426439&isnumber=30805

 

And John/DW.. have you looked at this?:

http://www.awaretechs.com/XCountry.html

[Horton]

Very cool  . . . yes and no. It costs 5 grand and only handles 3 Gs. I am not really sure how you use it. It is cool . . .  I would have to see what else those guys make. It looks like they are doing a lot of cool stuff

What I an thinking about is a unit that sits on the ski and records acceleration in 3 axis. That would show just what the ski is doing but I think that there is plenty to be learned there. I imagine seeing..... different amounts of roll and accel from 1/3/5 to 2/4/6. Is the ski faster after a fin change or a change in focus. How about side slip. If you could see the wake crossings in the data as I expect you would, you could check the boat times or see yourself getting earlier or later. The distance from 2 to 3 never changes . . . . .

The real question is if it works will it help me ski better?

[Horton]

On the really cheap

http://www.carolina.com/product/pasport+acceleration+sensor+2+axis.do?keyword=PASPORT&sortby=bestMatches# #

 

 

[Tom Henderson]

So this topic hasn't been brought up in a while, so i thought I would give it a go. All I want is a GPS tracking device to put on my ski right in front of my front boot. Im not all concerned with roll axis, but just being able to know where I am at (or actually where I was at) in the coarse I think could be a great learning tool. Just imagine being able to take a set, one 35 was very hard, and then the next 35 was the easiest you have ever run. Now you head back to the dock, plug the GPS unit into your computer and wala you can see the data on your computer that on the easier pass you were making S's where on the harder pass you were making Z's.

 

There has been a lot of talk about leading your turns with your hips CoM, but less emphasis has been put on where you are actually going. To be the most efficient in the slalom course we always need to ski a sustainable line, if not we will be fighting the boat all the way down the lake.

 

Any ideas where to get an accurate waterproof tracking device, if we can get boats to get actual times using GPS Im sure that we can get an accurate account to our line in the course. I want one. Love life. (3 weeks to go till the start of the season)

[Tom Henderson]

I swear to god that there are paragraphs in there when I clicked "add your comments"

[DW]

The difference in cost between a single channel output unit and a multiple channel output unit is negligible for adding several of the mentioned channels.

[Horton]

As for the comments... yea I know. Sorry about that.

[Phil2360]

So who out there knows a bit about programming?

What someone could do is look at the programs that are out there for N95 Nokia mobile phones.

They have a 3d accelerometer  in them & I've got an application on mine that makes graphs,

you can see it here:- http://www.youtube.com/watch?v=q_thmuDp06o 

If someone could modify this code a bit (It's provided & in something called Python), so that the data is actually being recorded instead of just displayed then we would have something that could be fun to play with for a starting point. N95's seem the be common out here, all you'd need would be a small tupperware container to waterproof it, & stick it inside your vest.

 

Phil

[WadeWilliams]

We will have GPS data acquisition available at SkiTek in the fall.

 

http://www.proskicoach.com

[Tom Henderson]

Wade I wanna play with it, you skiing looks sic on your site. Im stoked for the summer. See you soon