CARV Digital Ski Coach - used by a carving snowboarder - Review

[SunSurfer]

This review has been updated after additional information was received from the CARV data team. The significant changes are in the "Tech stuff" section.

https://www.facebook.com/share/p/ow5tShXg4DCPBooG/

(see above Facebook post for some images from my early runs with the CARV app.)

I bought a Version 2 CARV Digital Ski Coach setup in mid 2024 for use during a 3 week carving snowboard trip in New Zealand in August. I knew that CARV is planning to release new tech in the Northern hemisphere Autumn 2024 but that was going to be too late for me, and the set I bought came with one of the few remaining lifetime licences.

For the purposes of the review I rode UPZ RC10 boots with mondo 29 Intuition Pro Wrap liners. I bought the large CARV senors and these fitted the boot shells without problems. I remoulded the liners after fitting the CARV sensors and boot fit and performance were unaffected by the CARV units.

Binding angles ranged from 45 rear / 50 front with 2 degrees inward cant on a wide twin tip, to 75 rear / 80 front with 3 degrees outward cant skwal style, but most riding was done with a fairly conventional 60 rear / 65 front with 6 degrees of heel / toe lift and no cant on both feet.

Riding was tracked mostly at Roundhill, with single days at Mt Dobson and Cardrona ski fields. All fields were in New Zealand.

Setup

The boot top transmission units charged quickly, the supplied USB-A to proprietary connector cables are the only option for charging. Charge levels are shown in the phone app and CARV say they are able to do 3 full days riding without recharge. I charged mine every couple of days and it looked like they could have done 3 without problems.

I tried the CARV app on a Nokia 6.1 phone and a Samsung Galaxy A51 phone. No matter how I tried I couldn’t get the A51 to provide GPS data to the app so missed 2 days of location data, whereas the Nokia worked without problems. See the CARV website for an up to date list of compatible devices.

On your first use the app calibrates the boot sensors for motion and force. Motion calibration is done with the boots off and still. Force calibration has the boots on, buckled, and lifted off the ground one boot at a time. Over the 3 weeks I was using the system I had to recalibrate one boot once for motion, and one or both boots maybe 3 or 4 times for force. Most days however, a check of the indicator in the app showed that the boots were ready to use from the start, even if I had charged the transmission units the night before.

Did CARV use improve my riding? YES.

Because I was snowboarding the coaching hints from the app weren’t going to be relevant so I rode in Free Ski mode without audio feedback and reviewed my data in the app at days end.

Of the 12 metrics that the app tracks the following were useful to me as a carving snowboarder

Edge Angle
Progressive Edge Build
Turn Shape
G Force

There are also curved turn graphics for Edge Angle and Pressure that show how these change over the course of your Right and Left turns. These were probably the most useful and clearly showed from my first day with GPS data that my Right (Regular stance toeside) turn was weaker than my Left. Both angle and pressure levels were lower on the Right, as were the individual turn SkiIQ values.

In my carved turns pressure levels are highest on my inside boot at the point where the board turns away from the fall line on the exit path from the turn. This is the point where G-forces are highest. Pressure levels in the outside boot are low throughout the turn, reflecting that the outside foot is almost lifting up the outside edge, rather than pressing down on the inside.

Over the course of my trip I was able to improve my Right turns and more frequently match the Left turns for Edge Angle and Pressure on the curved graphics. This was by both consciously angling over earlier on the Right, and by accentuating medial knee movement of the knee on the outside of the turn i.e. Left knee moving across for a Right turn.

My (for what it’s worth) best SkiIQ rose from 129 on the first day of the trip to 136 by then end. I say “for what it’s worth” because SkIQ is a metric designed for skiers. According to the app my “skis” are not parallel, my edge similarity is poor, I put pressure on the wrong ski, and my fore/aft balance is all wrong.
Despite that, SkIQ still tracks upwards as the quality of my carved snowboard turns improves. I tried a series of 4 runs on the same Green rated, freshly groomed slope, with incremental improvements in turns. I went from skidded turns, to gentle carves with low edge angles, to higher edge angles and tighter turns, to full effort. Each step produced a significant rise in the rated SkiIQ for the run.

My Progress tab

To the right of each metric score in the app is a small arrowhead. Tap it and a new page opens up to tell you about the metric. There is a My Progress tab here, tap that and your best 5 day scores for that metric are averaged and your progress since you started presented.
I made progress for all 4 metrics I noted as useful above. But I have room to improve.
My Progress average edge angle was 56 degrees for the trip while I recorded run max. edge angles as high as 73 degrees. My Progress trip average G-force was 1.9G, close to my best run average of 2G. My best run SkiIQ was 136, but I found individual turns with SkiIQs over 140.
In general terms, turns with higher speeds, edge angles, and G-forces generate higher SkiIQs.

Tech stuff

The CARV app needs at least 10 turns to make a “run” and calculate the metrics.

From what I can glean from my data, the app and website, and my conversations with the CARV team, in general terms the accelerometers in the sensor track edge angles and sensor positions relative to the overall direction of motion. The Edge Angle and G-force run metrics are probably run averages, rather than mode or median values.

------------- The CARV data team replied to some questions after this review was first written.

Edge angle is measured by the absolute tilt of the insert around its long axis. G force is also measured relative to the change in direction of the long axis of the insert. The overall working assumption, not unreasonably, is that the inserts are in ski boots aligned with the long axis of skis.

Edge angle and G force are measured  for each turn in a run.
Max edge angle for a run is the maximum measured turn edge angle of the "outside ski".
Edge angle for a turn is the average of the maximum edge angles of both inside & outside "skis".
Run edge angle and G force are the median values of the run set of each metric.
--------------
The effect of the binding angle, lift and canting on the edge angle measurement can be worked out, and I confirmed what follows with bench testing with a board, wedges, and a phone runnning a clinometer app.
measured edge angle / cosine([90 - binding angle] degrees) = actual edge angle
e.g. for my binding angle of 60 degrees and a max measured edge angle of 73 degrees
73 / cosine(30 degrees) = actual edge angle
73 / .866 = 84 degrees

The 6 degrees of lift I use on each foot makes about a +/- 1 degree change to the measured edge angle. This is an effect that could be neglected except by the most obsessive data nerds!

Any binding canting will be change the baseline of the edge angle measurement for that binding.

A physics grad could probably explain how to calculate the corresponding compensation for the G-force calculation. That's beyond my maths knowledge.

The curved graphics in the app for Edge Angle and Pressure are coloured based on relative values rather than absolute values. So dark areas represent where the high values were for that run rather than whether the values were absolutely high or low.

After the more skilled of my riding companions crashed into me while shooting GoPro footage I elected not to try out the CARV Video Coach feature, where a mobile phone video can be linked to run data.

Overall Impression

This is written after some time and reflection on the data, and email conversations with the CARV team, after my trip finished.

CARV data helped me improve my snowboard carved turns. The techniques used to improve came from elsewhere.

If I was back on snow now I would probably try Monitor Mode for each of the 4 metrics I found useful. The Edge Angle Challenge would be fun too.

CARV collected useful data at all the binding settings I used (see above).

CARV would, in my opinion, be most helpful to beginner & intermediate riders wanting to progress, because it would enable them to track progress. However, the lack of widely accepted carving coaching tips to help them make progress is an issue. CARV data could potentially inform the development of coaching materials.

What would I like to see in CARV?

Max Edge Angle in the run summary data.

A computer version of the app, much like how Strava have both a phone app and computer views of users data. This would allow easier individual turn analysis.

Users able to view edge angle graphs for their turns. Examples of these are currently shown on the CARV website. The examples shown appear to split apart the inside and outside ski data to help see differences, but the extent of the offset in the data is not made explicit (looks like +/- 10 degrees).

And, pigs might fly, that there would be enough interest from the carving snowboard community to make it worthwhile for CARV to develop a coaching version for snowboarders who want to carve.

What about the new tech?

Some months ago I got the chance to test the new website for the new tech available Northern hemisphere autumn (see CARV website for the waiting list). It’s likely to be a boot top unit only with no sole pressure sensor. This likely to be more robust than the current setup where the reinforced flat cable between the sensor and transmitter is a potential point of failure. No boot sole sensor also means absolutely no effect on boot fit and no need for 3 different size sensors. A boot top only unit would be easily swappable between boots. What the effect would be of the greater range of motion in use of hard snowboard boot cuffs on data capture is unknown. Pressure data would not be available, but this may not prove to be a major loss. It appears that edge angle and G-force are some of the best indicators of a quality carved turn.

Edited September 6 by SunSurfer
additional information

[SunSurfer]

Friday 6th Sept 2024 evening (NZ time)
The review has been updated after additional information was received from the CARV data team. The "Tech stuff" section has been significantly changed.

[st_lupo]

Thanks for the update.  I was wondering about that edge angle measurement given there was no calibration that could correct for binding angles.  

Lots of potential if they would ever do some simple SW mods to allow it to measure snowboard stuff (don't really care about the coaching feedback).

There's two types of people this would appeal to 1)people that want to improve their technique.  2)people that want to endlessly adjust their equipment to find an optimal setup.  I hesitate to think about which category I would fall into...

[SunSurfer]

@st_lupo Laughing with you because I love fiddling with my setups and trying different stuff!

I'm pretty sure I'm more in the first group (improve) after my experience this year, because I'm sure I have room to improve.
But the ability to measure that improvement in edge angle, G force and turn symmetry is something I really value.
That also allows you to actually tell if a change made to riding setup or technique actually improves the carve.

I not sure it would necessarily help extreme carvers build technique.
Racers might need to actually see edge angle and G force graphs to work on their stivot / carve / early finish turns.

Edge angle calculations at low angles (duckfoot stance end of the range) are likely to be less accurate given the way this CARV tech iteration works.