GNSS Observations \rho_{S,f} = r_S + c\left( \Delta t_s - \Delta t_R \right) + T_S ρ S , f = r S + c ( Δ t s − Δ t R ) + T S + b^\rho_{S,f} + b^\rho_{R,f} + I_{S,f} + M^\rho_{S,f} + \epsilon^\rho_{S,f} + b S , f ρ + b R , f ρ + I S , f + M S , f ρ + ϵ S , f ρ \phi_{S,f} = r_S + c\left( \Delta t_s - \Delta t_R \right) + T_s ϕ S , f = r S + c ( Δ t s − Δ t R ) + T s + b^\phi_{S,f} + b^\phi_{R,f} - I_{S,f} + \lambda_f N_{S,f} + M^\phi_{S,f} + \epsilon^\phi_{S,f} + b S , f ϕ + b R , f ϕ − I S , f + λ f N S , f + M S , f ϕ + ϵ S , f ϕ HARDWARE BIAS IONOSPHERE DELAY CARRIER AMBIGUITY MULTIPATH EFFECTS FREQUENCY INDEPENDENT EFFECTS