Hi, Does anyone has experience using accelerometer on a ship/vessel to detect whether the vessel is moving or stationary? The difficult part is that I took some samples at 6Hz and found that all X/Y/Z axes have accelerations going positive and negative. The pattern is exactly the same when the vessel is moving and stationary. I suppose these are caused by ocean waves. The reason that I have to use an accelerometer to detect movements on a vessel is that my device (a custom embedded system) goes into sleep/hibernation most of the time to save power and it only wakes up to perform some tasks after it detected movements. GPS consumes too much power and therefore it can't be powered on all the time. Actually I do not need to measure the speed, direction or position, all I need is to identify whether the ship/vessel is moving or stationary at sea. Accelerometer works fine on land, but not at sea probably due to the random ocean waves. I have also considered using a gyroscope, however, it is too expensive. Any suggestions?