Sports vs Strava Data — TomTom Community

Sports vs Strava Data

Msatoh21Msatoh21 Posts: 3 [Apprentice Traveler]
data on TOMTOM Spark watch vs Strava is way off. - Did a century ride this weekend with both the watch and strava/phone turned on. strava gave me 3,102 cal / 1,543 elev. gain, Spark shows 6,125 cal / 7,714 ele. gain. rest of the data are close (time / distance). checked with other riders and the data from Strava matches the rest. 1) how do I adjust/fix the data on the watch. 2) if not, is the watch reliable?

Comments

  • tfarabaughtfarabaugh Posts: 16,347
    Superusers
    You are comparing apples and oranges a bit here as the two devices have different measurement devices and calculation algorithms but that does seem way off. On the calories I would make sure that you have the exact same personal stats in both devices, if the weight or gender or something is off it will be completely off. you also need to look at how they are calculating calories, are they using HR or METs or another method. The watch uses a METs calculation in cycling mode, not HR which takes your personal stats into consideration. If you were using freestyle mode it will use HR for calories. I am not sure what the Strava app uses. For elevation, they are both likely using a digital elevation model after the fact to come up with elevation and that will depend on the integrity of the GPS data collected and the quality of the DEM used. It also depends on whether they factor in all elevation gain or only over a threshold. During a relatively flat stretch of road you may be constantly going up and down a few feet at a time and some devices count every bit of ascent while others ignore all the small changes.

    You can go into MySports and edit any of the data that you like (there is nothing to change on the watch itself, the data is cleared except for summary stats for the history) as long as you are confident it is correct. According to a quick Internet search:

    Bicycling 12 to 13.9 mph is a “moderate effort,” according to the Wisconsin Department of Health. When you bicycle 12 to 13.9 mph, you burn about 53 calories per mile if you weigh 190 pounds, about 43 calories per mile if you’re 155 pounds and about 36 calories per mile if you’re 130 pounds.

    So either calorie total could be right depending on your weight, age, etc.. It may be worth going to an online calculator and insert the data and see what it tells you to see which one is more accurate. For the elevation, compare the two elevation charts and look for any weird data or large gaps. Over 100 miles, unless you were on a totally flat course, 1,500 feet seems low at 15 feet of gain per mile. That is little more than a few speed bumps. 7,700 may be too far the other way, though. The truth may be somewhere int eh middle.

    You can also import the fit file from TomTom into Strava and see what it comes up with, as it will recalculate everything based on their own algorithms.

    I hope this helped answer your question. If so, please mark it as a solution so others can look for it if they have the same question.
  • Msatoh21Msatoh21 Posts: 3 [Apprentice Traveler]
    Thanks for the in-depth response.
    I'll adjust the data on My Sport but..if the data is way off, not sure if I can rely on the watch.
    The ride was fairly flat route from Culver City to Santa Barbara, (google shows a 1470 ft elevation)
    turned HR off Spark to preserve battery life.
    I'm 5'11" 171LB, average pace at 14mph.

    will try to inport the fit file and see how it compares.
    thanks again.
  • tfarabaughtfarabaugh Posts: 16,347
    Superusers
    When I put you stats into an online calculator at bicycling.com it comes up with around 5,200 calories burned (the pace choices are 12-14 mph and 14-16 mph so I averaged the two) so the truth is likely somewhere in the middle (although the watch is closer). All the calculators use METs, which are scientifically tabulated tables of energy expenditure for a specific activity at varying paces. It uses the MET factor along with your personal stats to come up with an energy expenditure number. Depending on where you fall within the average used to compile the tables it may or may not match you exactly. And since it is not looking at HR it has no way of knowing if your level of effort was beyond what is typical at a given pace, which is what the METs are based on. Ultimately, any devices calorie number is just a guess, regardless of method. HR based is only accurate within a relatively small range of HRs at submaximal efforts, while METs based does not take into account elevation change and HR. You just have to pick a method you agree with and stick to it. I personally use the average HR data and put it into an Excel spreadsheet with the standard HR formula (or an online calculator that calculates using HR), this way I am not relying on the watch to calculate calories and will be consistent regardless of device as I am just using the raw HR data. The TomTom in Freestyle mode (the only one that uses HR) is right on these numbers (more so than my Suunto which also uses the same data but applies an algorithm trying to estimate R-R values).

    For elevation, I am not sure why the watch was so far off. Examining the elevation charts side-by-side may shed some light on that. It may have hit a bad GPS point that threw it off at some point.

    I hope this helped answer your question. If so, please mark it as a solution so others can look for it if they have the same question.
  • Chrisski33Chrisski33 Posts: 4 [Apprentice Seeker]
    Ive noticed a difference in distance too between strava and my watch when on bike and im using the tom tom bike cadence and speed sensor.
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