  Vector magnetometry provides more information than scalar measurements for
magnetic surveys utilized in space, defense, medical, geological and industrial
applications. These areas would benefit from a mobile vector magnetometer that
can operate in extreme conditions. Here we present a scanning fiber-coupled
nitrogen vacancy (NV) center vector magnetometer. Feedback control of the
microwave excitation frequency is employed to improve dynamic range and
maintain sensitivity during movement of the sensor head. Tracking of the
excitation frequency shifts for all four orientations of the NV center allow us
to image the vector magnetic field of a damaged steel plate. We calculate the
magnetic tensor gradiometry images in real time, and they allow us to detect
smaller damage than is possible with vector or scalar imaging.
