The attitude of a human eye with respect to a head coordinate system is monitored
for the purpose of determining the visual axis and for providing a control signal
for control purposes such as controlling an image. The position, attitude or both
of the head with respect to a reference frame may also be monitored for translating
and/or transforming the monitored visual axis into other reference frames. Transformations
and translations of the visual axis into additional reference frames are also disclosed.