Hey everyone. I'm working on a project that will incorporate a wireless accelerometer on a model rollercoaster. My issue is that we wish to take the accelerometer data and integrate it to give us our velocity through any part of the ride. This in turn will help us determine losses, etc. My issue is that the rollercoaster has loops and hills. It would be easy to integrate the 'X' accelerometer data on a flat plane, however since the coaster will be angled up or down depending on the part of the ride, you'd have to consider the affect of gravity in the 'x' direction when the car is tilted. This can be done easily with vectors by hand, but we need to be able to integrate in real time using pure accelerometer data (which is in normal values such as 'x=1.00 y=.40'. Attached is a photo explaining my axises. I know the Wiimote does something like this. My guess is we'd need to determine the angle of the bank and then take out the gravity aspect. That could become hard because through a loop, the Y axis data will be very large (along the lines of 5-6G's), so you cannot just compare the X and Y data and do some math there. Any ideas?