TomTom Spark 3 watch speed/distance inaccurate compared to mobile phones

Chester71 Registered Users Posts: 2
New Traveler
edited January 24 in TomTom Sports

For years I used my Nexus 5X mobile with Nike+ app on it for running, listening to my favorite music and getting periodic information during my runs on speed, distance etc. Since this happens only every 500 meters, I decided I needed a watch to see real time speed. Or tempo. I bought the tomtom spark 3. To my surprise, both tomtom and LG Nexus seem to hardly every agree. While the nexus shows stable information, the tomtom shows strange little dips in tempo and after about 10 km the difference between both is about 150-200 meters. Where the tomtom is always more 'negative'. Now, I was willing to believe that the great TomTom with years of GPS experience must be more accurate, but after a few months I have to say I think it's not. Examples; I press start on both phone and watch almost simultaneously, while I started running already. This is to prevent ramp-up information. The Nexus does exactly that, after the running it shows a speed of 5,5 min/km from the first second. The tomtom however still 'creates' some kind of ramp up of about 180-200 meters. God knows why. Since at the end it's about 180 meters off, the difference per km between the watch and phone is usually around 5 second per km, a lot for me.
I've been reading around where this could come from and where these occasional dips in speed come from, while I run in open farming fields with nearly free view to the horizon. Obstructions can not be discussion. To prevent having to strap a gps antenne to my head, why does the watch seems to be less accurate? What could I do to improve?
NB. I update the watch (gpsfix) 2 times a week and giving it some time before running to find some more satellites.

Thank you for suggestions.


  • lampard
    lampard Administrators Posts: 6,006
    Hi Chester,

    Welcome to the Community m& Sorry about the delay in response!

    Since you mentioned that you ran in open farming fields, the difference in calculation seems to be bit much. This can be a problem with the firmware image installed on your Spark watch, I would suggest a factory reset which will clear the watch and reinstall a fresh image.

    Once you perform a reset, give it a test run & see if it improves the accuracy. Let us know the outcome!