Optimal estimation of layback distance for marine towed cables

The estimation of towfish layback distance is usually performed with computer programs that implement numerical integration of system differential equations. The system dynamic model usually includes an estimate of coefficients of drag and velocities of the towfish and cable. Often these quantities are unknown or estimated with a great deal of uncertainty. The technique reported uses an optimization approach to circumvent the estimates of critical parameters and instead uses accurate measurements of towfish depth and length of cable paid out. A criterion is formulated and minimized using a simple gradient-optimization method. The simulation results indicate that the method works well and can be implemented in a real-time data-acquisition system