Systems, methods and computer program products are disclosed for medical navigational guidance systems. In one example, intra-operative leg position measurements are provided during hip arthroplasty. An optical sensor couples to a pelvis and a target couples to a femur in alignment with the sensor, which provides positional signals to a processing unit for determining a relative position of the sensor and target. The processing unit uses a baseline measurement of leg position and a map to calculate and display position measurements in real time. The map is defined through a registration range-of-motion procedure where instructions are presented to move the femur in at least two planes to generate signals to calculate the map. Leg position may be leg length, offset or anterior/posterior position. The map is used to present the leg position measurements in an anatomical, rather than a sensor, coordinate frame.