Walter Purvis Smith CB OBE (March 1920 – 11 December 2018) was an English land surveyor notable for being the first civilian Director General of the Ordnance Survey, from 1977 to 1985.
In 1957 he returned to his earlier interest in the Territorial Army where, on promotion to Lieutenant-Colonel, he assumed command of 135 Survey Engineer Regiment TA.
This was followed by a mission to Nyasaland (now Malawi) to measure that country's base-line and reconnoitre a major triangulation chain from Mount Mulanje in the south, then 600 miles northwards to Mbeya in southern Tanganyika (now Tanzania).
For two years he travelled extensively, on behalf of the UN, supervising projects of institution-strengthening or mapping in support of various countries' development programmes.
Following his retirement from the Ordnance Survey, Smith was deputy chairman of an independent committee appointed to review the handling of geographic information in the UK.