Dear Hamid Reza,
Yes, removing the azimuth angle perturbation (Δδg) as a state involves removing a row and column from the state-space model. Then, with a little manipulation you can convert the resulting 3-state model from using Δωg, Δδtg, and Δωtg as states to using Δωt, Δωg, and Δδtg as states. That is: Δωt = Δωg + Δωtg.
Best regards,