1. A system for mapping a magnetic field in a volume of interest, the system comprising: a magnetic field transmitter, generating a magnetic field in said volume of interest; at least one freestanding magnetic field detector, operative to freely move within said volume of interest, said at least one freestanding magnetic field detector acquiring measurements of the flux of said magnetic field at a plurality of poses; at least one pose information acquisition module for measuring information related to the pose of said freestanding magnetic field detector; and a processor, coupled with said magnetic field detector and with said at least one pose information acquisition module, said processor determining pose related information respective of at least a portion of said measurements of the flux of said magnetic field according to said information related to the pose of said freestanding magnetic field detector, measured by said at least one pose information acquisition module, said processor estimating the entire set of parameters of a magnetic field model template according to said magnetic field flux measurement and the respective pose related information thereof, said processor incorporating said entire set of parameters into said magnetic field model template, thereby determining said magnetic field model, wherein, said entire set of parameters includes the coefficients of said magnetic field model, the order of said magnetic field model, the number of the centers of expansion and the locations of the centers of expansion of said magnetic field model.