Pearson was born in Kensington and educated at St. Paul’s School and the Royal Military Academy at Woolwich. He was commissioned as a Second Lieutenant in the Royal Engineers in 1893. Pearson saw service on the Tirah Campaign (1897-98) in India and at the relief of Peking [Beijing] (1900-1902). During 1902-03 he led the Anglo-Liberian Boundary Commission and surveyed the sources of the Niger River. In 1903 the engineer commanded the Colonial Survey Section operating in Sierra Leone. Pearson joined the Egyptian Army in early 1905 and soon after became Director of Sudan Surveys.

Pearson’s career in the Sudan required surveying areas of the vast territory little known to westerners. In 1906 he worked upon the construction of Port Sudan [Būr Sūdān], and surveyed the region between the Blue and White Nile Rivers known as Gezira [Al-Jazīrah], so that cotton cultivation could be developed. In 1910 he delimited the boundary between the Belgian Congo and the Sudan. The following year saw Pearson mapping Kordofan [Kurdufān]. In 1912 he participated in an expedition against the Beir people on the Abyssinian border and surveyed the Sobat and Pibor Rivers. In 1914, Pearson was engaged upon the Blue Nile Survey, and other topographical work linked to the construction of the dam at Makwar and the Gezira Canal, to make more efficient use of its flood waters.

During the First World War, Pearson was posted to the Sudan, Arabia, and Palestine where his service with the Desert Mounted Corps was recognized with the award of the D.S.O. and promotion to lieutenant-colonel. In 1917 he travelled to Addis Ababa to present Tafari Makonnen (later Ethiopian Emperor Haile Sellassie) with the Grand Order of St. Michael and St. George. After the conflict, he resumed his work as Director of Surveys and in 1919 married Blanche Grigg during leave in England. In 1921 Pearson represented Britain on the Anglo-French Commission which set the Wadai-Darfur boundary between the Sudan and French Equatorial Africa. During this time, he contracted blackwater fever in Darfur and died at Um Dafog on 28 Dec. 1922.

Pearson had become a member of the Royal Geographical Society in 1907 and published several papers in its journal. In 1913 the society bestowed the Murchison Award upon him for his exploration of the Sudan. Pearson was a very sociable man and a prominent figure in Khartoum society, organizing sporting, musical and theatrical events.