This paper provides a description of MOTAN, an inertial motion measurement system that has been used to measure ice-induced global impact forces on ships since the year 2000. Measurements from three ships are used to show that MOTAN measures whole-ship motions reliably, and that those motions can be used to determine global impact forces on ships with reasonable accuracy. Data from the CCGS Terry Fox are used to show that MOTAN and two other, independent instrumentation systems measured impact forces that were in good agreement. Having demonstrated that MOTAN is a viable means of measuring global impact forces on ships, the discussion focuses upon more recent efforts to develop an autonomous MOTAN, i.e. a system that operates unattended during a ship’s entire operating season. To date, the autonomous MOTAN has been installed on two ships: CCGS Henry Larsen and the M/T Véga Desgagnés, with the objective of using the data to determine statistical information about the magnitude and frequency of global loads that a ship experiences during its operating season.