Magnetic anomaly surveillance system using spherical trilateration

A magnetic anomaly surveillance system, comprising:

• a plurality of time-synchronized, magnetic field sensing nodes arranged in an array with respective ones of X,Y,Z magnetic sensing axes of each of said nodes being mutually parallel to one another in said array, each of said TM nodes at a known location in a coordinate system with one said known location serving as a reference location in said coordinate system;
• a processor coupled to each of said nodes for
• generating a scalar magnitude of a magnetic anomaly field measured at each of said nodes, wherein each said scalar magnitude is indicative of a spherical radius centered at said known location associated with a corresponding one of said nodes,
• generating a comparison between each said scalar magnitude and a threshold value, and
• determining at least one magnetic anomaly location in said coordinate system relative to said reference location via a spherical trilateration process that uses each said spherical radius and each said scalar magnitude associated with selected ones of said nodes for which said threshold value is exceeded,
• determining a magnetic dipole moment at said at least one magnetic anomaly location;
• and
• at least one output device coupled to said processor for outputting data indicative of said at least one magnetic anomaly location and said magnetic dipole moment.

A magnetic anomaly surveillance system, comprising:

• a plurality of triaxial magnetometer (TM) sensors with each of said TM sensors having X,Y,Z magnetic sensing axes, said TM sensors arranged in an array with respective ones of said X,Y,Z magnetic sensing axes being mutually parallel to one another in said array, each of said TM sensors at a known location in a coordinate system;
• a processor coupled to each of said TM sensors for
• generating a scalar magnitude of a magnetic anomaly field measured at each of said TM sensors, wherein each said scalar magnitude is indicative of a spherical radius centered at said known location associated with a corresponding one of said TM sensors,
• generating a comparison between each said scalar magnitude and a threshold value,
• generating a differential quantity for pairs of said TM sensors, each said differential quantity defined by a difference between said scalar magnitude for each of said TM sensors associated with one of said pairs,
• determining at least one magnetic anomaly location in said coordinate system via a spherical trilateration process that uses each said spherical radius and each said scalar magnitude associated with selected ones of said TM sensors for which said threshold value is exceeded, wherein, when each said differential quantity is approximately zero, said processor does not determine said at least one magnetic anomaly location via said spherical trilateration process when said threshold value is exceeded, and
• determining a magnetic dipole moment at said at least one magnetic anomaly location;
• and
• at least one output device coupled to said processor for outputting data indicative of said at least one magnetic anomaly location and said magnetic dipole moment.