(Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1975-01)
Durham, James Leighton
A high resolution acoustic navigation system for ocean use
is being developed at the Woods Hole oceanographic Institution.
The system can yield navigation fixes with respect to a bottom
moored reference net with accuracies (on a fix to fix basis) of
a few centimeters. In order to use the system to best advantage
a survey is required to determine precisely the relative
positions of the net elements. Each element combines a pulse
transponder with a continuous wave (CW) beacon. Accumulated
phase (Doppler shift of the CW beacon) between survey points is
measured as well as acoustic travel times between survey points
and transponders. Non-linear regression techniques are employed
to develop a maximum likelihood estimator for net element
positions based on these phase and travel time measurements.
An approximate error covariance matrix is generated and an
optimum choice of survey points is indicated., The combined
system, using these selected locations for performing the survey,
can yield reference mooring coordinates with error of ±1 meter.
Improved precision appears to be limited by inaccuracies in the
pulse and Doppler measuring system.
