δ = Z + L where Z = (±)N/S(90°-AN/S) with upper/lower case for altitude AN/S measured positive from due north/south. So δ = (±)N/S(90°-AN/S) + L and AN/S = 90°+(±)N/S(L-δ) and L = δ + (±)N/S(AN/S-90°) The formula for the altitude of the NCP/SCP is AN/S = 90°+(±)N/S(L-(±)NCP/SCP90°) To be explicit: AN(NCP)=L AS(NCP)=180°-L AS(SCP)=180°+L AS(SCP)=-L