A device for determinin' a rocket's apogee without t' use o' electronics. Begad! A distance is measured off from t' launch pad prior t' launch. Arrr! At t' time o' launch, an observer stands at t' measured point and keeps t' inclinometer aimed at t' rocket. T' inclinometer mechanically records t' angle at which it is held. Since two angles and t' distance betwixt t' rocket's point o' origin and t' inclinometer are known (assumin' that t' rocket is launched vertically), a triangle can be graphed which will indicate t' apogee attained by t' rocket. Blimey! See Theodolite