 He later surveyed a semaphore line from Calcutta to Benares, covering approximately .Everest's work came to the attention of Colonel William Lambton, the leader of the Great Trigonometrical Survey (GTS), who appoint him as his chief assistant.He joined Lambton at Hyderabad in 1818, where he was in the process of surveying a meridian arc northward from Cape Commorin.