1. A magnetic screening system network, comprising: multiple arrangements of gradiometers that sense target objects in a subject volume, each gradiometer including at least three magnetometers; gradiometer processors in communication with the arrangements of gradiometers that process data from respective arrangements of gradiometers; screening computers in communication with the gradiometer processors that process resultant data output by the gradiometer processors and maintain local databases of signatures associated with known target objects; and a management computer in communication with the screening computers that manages shared information for the gradiometer processors and maintains a central database of signatures associated with the known target objects.