The availability of Global Navigation Satellite System (GNSS) receiver is challenged by urban shading and electronic jamming, which would induce receiver out of work and obstruct applications of GNSS. The collaborative navigation methodology for GNSS group users was studied, and user assistance for urban environments and generalized adaptive digital beamforming (ADBF) based on dynamic synthetic aperture for anti-jamming was proposed. The architectures of decentralized and distributed networks were described, and assisted positioning methodology was presented. In addition, the application of double frequency, elimination for direction of arrival (DOA) ambiguous was presented for generalized ADBF, which could avoid grating lobe induced by large spacing antennas. Simulation results demonstrated that, for 60 seconds GNSS signal outage, the positioning error of user assistance could be reduced from 280 m to about 30 m, compared to inertial navigation; and generalized ADBF removed the grating lobe effectively.
