Ski Tracking App Accuracy or Lack thereof

ski_it

I’m aware of the general inaccuracies in GPS which has many causes, such as strength of signal, type of receiver & programming, etc, etc…which can lead to sizable errors in these tracking apps. Then there is the app program itself which are not all created equal.  This week I skied side by side with someone with close to the same equipment and app and the difference in numbers is surprising. 1878 foot difference in vertical. One phone is a iPhone 5s with Ski Tracks by Core Coders V1.6.3 the second is an iPhone 6 with Ski Tracks Lite by Core Coders V1.6.3.The numbers are all over the place. We rode the West lift 3 times & the Rocket 20, so if the Rockets reported vertical of 875 *20=17500 minimum, but one phone reports 17063 total with 882 delta. The other sounds more correct at 18941 total but then it has a 1034 delta for an 875 hill. And I’ve read online that the speed numbers are the most inaccurate part of these GPS apps. Also, if you happen to have this particular app be aware that it will not count runs under 280 ft.From their site:“The reason Ski Tracks may not reporting the run count correctly is that the elevation of your resort is too small to be registered as run. If the run and lifts are less than 280ft/90m this can cause the current algorithm issues with regards to counting runs and lifts.To fix this issue we are doing a number of new things:

An improved lift detection algorithm.

Improved GPS detection for smaller mountains.

Lift database to find lifts and name them.

Track editing to add lifts in.

Any existing tracks will automatically be updated and the run count re-calculated. All of these new features will be made available soon in a future version of Ski Tracks.”

joshua_segal

I have similar issue with the Ski Tracks app.  In the attached example, 71 on the Rocket, 3 on the West Double and 2 on the Valley.  Using 860 vertical as a conservative number for the rise of the Rocket, I estimate it short-changed me by about 4000 feet.

ski_it

What’s your delta estimate on the other lifts?

joshua_segal

<blockquote class=“Quote” rel=“ski_it”>What’s your delta estimate on the other lifts?</blockquote>

Doesn’t matter what ski area I’m at.  It appears to be about 5%.  Part of it is the sampling frequency.  The faster I’m skiing, the less the vertical recorded per run.  When I take one run where I walk to the top and sit at the top to catch my breath for 5 minutes or so - and then hang around the base area to schmooze after the run, it usually reads accurately for that one run.

DrJeff

I run Trace snow on my Droid Turbo - my main face runs at Mount Snow are usually within 25 vertical feet +/- 1600 verts which historically has been the recorded vertical there.

Most of my runs, on any lift there with over 100 vertical feet record quite consistent day in and day out, generally in the +/-2% range.

The variables I have noticed, is if I take a prolonged stop to watch my kids race (it might break that singular run up into 2 runs) and sometimes if I do lots of traversing in 1 run, it tends to add +5% on what I’ve found to be that historical vertical for that particular run.

Speed wise - top end is a joke at times - when it says that I hit speeds 10-15mph faster than I used to be clocked at by radar gun in downhill races I used to do, while on 220cm DH race skis and in a speed suit, and currently I’m wearing bulky, non form fitting coats and not in a prolonged tuck to hit those speeds, I take the speed data with a BIG grain of salt

joshua_segal

<blockquote class=“Quote” rel=“DrJeff”>…  Speed wise - top end is a joke at times - when I says that I hit speeds 10-15mph faster than I used to be clocked at my radar gun in downhill races I used to do, while on 220cm DH race skis and in a speed suit, and currently I’m wearing bulky, non form fitting coats and not in a prolonged tuck to hit those speeds, I take the speed data with a BIG grain of salt</blockquote>

I don’t take the speed number seriously, especially when it showed my max in excess of 100 MPH on more than one occasion!

Most of the time, I ride lifts that exceed the minimum vertical to count runs, but at CM, it doesn’t record either the carpet or the Zero-G as runs.  I think I mentioned on another thread that when I skied Buck Hill, MN in Dec. 2015, that I logged multi-thousand feet of vertical, but zero runs.

ski_it

<blockquote class=“Quote” rel=“joshua_segal”>I have similar issue with the Ski Tracks app.  In the attached example, 71 on the Rocket, 3 on the West Double and 2 on the Valley.  Using 860 vertical as a number for the rise of the Rocket, I estimate it short-changed me by about 4000 feet.</blockquote>

Wow! Almost ten hours of skiing! I’m surprised your battery lasted that long out in the cold while duct taped to the bottom of a Rocket chair. ;)

JMaul

<blockquote class=“Quote” rel=“joshua_segal”>I have similar issue with the Ski Tracks app.  In the attached example, 71 on the Rocket, 3 on the West Double and 2 on the Valley.  Using 860 vertical as a conservative number for the rise of the Rocket, I estimate it short-changed me by about 4000 feet.</blockquote>

You Tiger, you.

ski_it

<blockquote class=“Quote” rel=“joshua_segal”><blockquote class=“Quote” rel=“ski_it”>What’s your delta estimate on the other lifts?</blockquote>

Yeah I would expect 5% or so but Mrs. Ski_it Jr & I skied side by side all day and sat at the same lunch table and our totals are 11% apart. WE had to be real close in speed as well. We did use different bathrooms but they are on the same level. TMI? She did ski more bumps than me.I was just wondering what the real West delta is so I can calculate the correct total. Would you know the true top elevation of the Rocket too?

rickbolger

You guys might want to look at the Trace app Dr. Jeff refers to.  While the speed figures might be optimistic, the distances and vert seem to be reasonably accurate, it records very short runs, and it’s a free app.

Did a screen capture of a very short recent run, 63′ vert at Windham

ski_it

Thanks, I may just do that. That MIGHT have worked at Gateway Hills.

Cannonball

I’ve been using the Trace app.  I’ve used it on 3 different phones. Lately I’ve been using it on an old throw-away tracphone that doesn’t even have a cell plan. It collects data during the day and I uploaded it when I’m at home on Wi-fi. I do this so that I’m not using up my primary phone’s battery life on the hill.  

I have found this app to be very accurate for all parameters. Just as an example, here is a screen shot from last Sunday. Even minor things like which side of the trail I was riding, or quick dips into the woods are accurate. 

DrJeff

Here’s my screenshot of my Trace activity from Magic last Sunday - you can see via the “2 new lifts” it created for me in my attempts to ski to the finish area where my daughter’s race on Talisman was, that it doesn’t just limit your “lift rides” to known lifts, but decent uphill climbing/hiking segments!!

I can assure you that they DIDN’T install any new lifts in the middle of the trees in The Hallows on skiers right of Talisman, or installed a lift on the bottom of Talisman from where Tali intersects with lower Wizard on up to where the finish area of the race was ;)

Although if they had charged for snowmobile rides up the bottom of Tali to the race finish area AND set up a Tiki Bar there, they probably could of made enough $$ off those 2 things alone to pay for the Green getting running!! Lol!! Lots of tired, huffing and puffing, thirsty, hungry sweaty racer parents in the finish area on Tali on Sunday!! :D <:-P

NELSAP

Trace is good, but I have noticed a 50-75′ variance on each run from the same lift. Sometimes it comes up with some “phantom” runs riding up a chairlift. The 50-75′ differences can add up to over 1000-1500′ of lost vertical for a whole day.

joshua_segal

<blockquote class=“Quote” rel=“JMaul”><blockquote class=“Quote” rel=“joshua_segal”>I have similar issue with the Ski Tracks app.  In the attached example, 71 on the Rocket, 3 on the West Double and 2 on the Valley.  Using 860 vertical as a conservative number for the rise of the Rocket, I estimate it short-changed me by about 4000 feet.</blockquote>

You Tiger, you.</blockquote>

I was wondering if anyone would notice.  That was in honor of my upcoming 71st birthday

ski_it

<blockquote class=“Quote” rel=“joshua_segal”><blockquote class=“Quote” rel=“JMaul”><blockquote class=“Quote” rel=“joshua_segal”>I have similar issue with the Ski Tracks app.  In the attached example, 71 on the Rocket, 3 on the West Double and 2 on the Valley.  Using 860 vertical as a conservative number for the rise of the Rocket, I estimate it short-changed me by about 4000 feet.</blockquote>

You Tiger, you.</blockquote>

I was wondering if anyone would notice.  That was in honor of my upcoming 71st birthday</blockquote>

Oh I noticed. It makes my old knees hurt just looking at that report. I just figured you were practicing for another milestone of sorts in another 4 years. 

ski_it

I know there must be an app for that, BUT I used my Ski Tracks App set to X-C activity to kayak almost 7 miles and it said I got 1551 feet of vertical. ;))

joshua_segal

<blockquote class=“Quote” rel=“ski_it”>I know there must be an app for that, BUT I used my Ski Tracks App set to X-C activity to kayak almost 7 miles and it said I got 1551 feet of vertical. ;)) </blockquote>

What did it get for max speed?

rickbolger

Awesome!  I did a search for you on Ski Tracks and watched the video

ski_it

<blockquote class=“Quote” rel=“joshua_segal”><blockquote class=“Quote” rel=“ski_it”>I know there must be an app for that, BUT I used my Ski Tracks App set to X-C activity to kayak almost 7 miles and it said I got 1551 feet of vertical. ;)) </blockquote>

What did it get for max speed?</blockquote>

5.4 mph. Avg 1.7. The graph looks like 3.5-1.5. The mileage looks about right. I tried one day as ice yachting and it got 980 ft vert, then another regular skiing it got 575 ft, all days similar mileage 5-6. Nice Rick! Although for me the section of the river I was in didn’t have that big a drop.