From my experience and work, I know that getting distance estimates just from accelerometer and gyroscope is an extremely difficult task, especially when you are swimming. I have also seen that even though an apple watch asks you to set pool length for indoor swimming, it is able to accurately show the distance I have swum in the watch but later adjusts it when you sync it with the app.

For eg, if I am in a 25m pool and I select a 25m pool before swimming, then if I swim only half of the pool, my watch shows that current covered distance is 12.5m but when you sync it with the app, it converts that to 25m since I had initially selected 25m pool. My problem is that, how did the watch know that I had swum 12.5m by then. It doesn't use the GPS for indoor swimming as far as I know. Only other option is dead reckoning with accelerometer, gyroscope and magnetometer which in my experience does a very poor job at it.

I have read may papers on how to do it but most of them use person's height and weight to estimate step length which they multiply with detected number of steps. Some tie the sensors on their foot to more accurately measure step length but that is not what I am looking at.

Does anyone know a reliable paper where I can see how to estimate distance for long swimming sessions.


1 Answer 1


Is in-door GPS sufficiently accurate that they know which pool you are in? Could they use a table/map of known swimming pool lengths and the acceleration impulse as you turn to count number of crossings?

  • $\begingroup$ The number of crossings can be calculated but I was asking about the distance calculation in between laps. For eg: , in a 25m pool, it shows distance from 1m to 25m as you swim the entire length. $\endgroup$ Jan 16 at 13:17

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.