A system for mapping a magnetic-field in a volume-of-interest comprising a magnetic-field transmitter, generating a magnetic-field in the volume-of-interest, a freestanding magnetic-field detector operative to freely move within the volume-of-interest, a pose-information-acquisition-module and a processor. The detector acquires measurements of flux of the magnetic-field at a plurality of poses. The pose-information-acquisition-module measures information related to the pose of the detector. The processor determines pose-related-information respective of at least a portion of the measurements according to the information related to the pose of the detector. The processor estimates the entire set of parameters of a magnetic-field model template according to the magnetic-field flux measurement and the respective poses-related-information thereof. The processor incorporates the entire set of parameters into the magnetic-field model template, thereby determining the magnetic-field model. The entire set of parameters includes the coefficients, the order the number and location of the centers of expansion of the magnetic-field model.