Magnetic relative position measuring system

A method of guiding a naval ordnance device to a target, comprising the steps of:

• (A) at a relatively long range from the target,
• (a) generating relative position data with respect to the target at said device by means of an active on-board target detection system and generating first guidance signals;
• (b) coupling said first guidance signals to a guidance system on said device;
• (B) at a relatively medium from the target,
• (c) repeating steps (a)-(b) and additionally determining the orientation angle of the target using the active on-board target detection system and coupling data of said relative position and orientation to a passive on-board target detection system;
• (d) measuring three mutually orthogonal components of the magnetic induction field of the target by said passive system;
• (e) calibrating a stored magnetic model of the target by said passive system using said data of said relative position and orientation of said target in step (c) and the orthogonal magnetic field components measured in step (d);
• and
• (C) at a relatively near range from the target,
• (f) repeating step (d) and determining the relative position of the target by said passive detection system from said three orthogonal components of the target's magnetic field, the calibrated model of the target, and an initial relative position trial solution from the active onboard target detection system;
• (g) generating second guidance signals by said passive target detection system;
• and
• (h) coupling said second guidance signals to said guidance system.

Apparatus for guiding a naval ordinance device to a target, comprising:

• (a) an active target detection system including means for generating acoustic data signals of said target at relatively long and medium ranges from the target;
• (b) means responsive to said acoustic data signals for generating signals of the relative position and orientation of the target;
• (c) means for generating first guidance signals in response to said relative position and orientation signals;
• (d) means for coupling guidance signals including said first guidance signals to a guidance system of said device;
• (e) a passive target detection system including magnetic sensor means for measuring and generating signals of three mutually orthogonal components of the magnetic induction field of the target at said medium and at relatively near ranges from said target;
• (f) means for storing a magnetic model of at least one said target;
• (g) means for calibrating said stored magnetic model by said signals of the relative position and orientation of said target and said signals of the orthogonal components of the magnetic induction field of the target;
• (h) means for generating signals of a new relative position of the target in response to said signals of three orthogonal components of the target's magnetic induction field and said calibrated model of the target;
• and
• (i) means for generating second guidance signals by said passive target detection system in response to said signals of a new relative position,
• (j) said second guidance signals being coupled to said means for coupling guidance signals to said guidance system.