CMU has released a new technical paper titled, An Analysis of the Human Odometer (PDF format) that may be of interest to anyone working on complex odometery problems in robotics. The CMU Human Odometer is a collection of sensors that form a personal navigation system intended for firefighters, police, or soldiers. The system includes a handheld computer that integrates data from a GPS unit worn on the head, an IMU worn on each leg below the knee and a fiber optic gyro worn on a belt at the waist. The sensor data is fused using an Extended Kalman Filter (EKF) to provide "accurate position information without reliance on external references".