It is, for a few reasons. For one, you need to be able to detect the period of stillness, and so how certainly you can detect that time window is a function of

It is, for a few reasons. For one, you need to be able to detect the period of stillness, and so how certainly you can detect that time window is a function of how long it is. Second, you need to be able to make a number of measurements from your IMU during the downtime. If you have an IMU that works at 20Hz and your period if stillness is 100ms, then you know you can get a measurement in. If your period of stillness is 10ms, then you can't.