US Patent 7653399 Wide area differential satellite positioning with local area updates

Wide area corrections are used substantially continuously. Local area corrections are used once or sparsely. For example, an initial position is determined with local area corrections. Wide area corrections are subsequently used. The initial position information is used in the wide area position determination to limit or avoid delay for convergence. Other sparse uses of local area corrections include verifying or updating positions based on substantially continuous use of wide area corrections.