Lieutenant D. M. Barbier, described as an engineer, was one of several surveyors and engineers employed on an extensive mapping programme at the Cape under the direction of Governor C.J. van de Graaff* during the latter's term of office from 1785 to 1790. Barbier came to the Cape from Holland, probably with van de Graaff in January 1785. With L.M. Thibault* and the governor's son, S.W. van de Graaff*, he drew up plans for new fortifications, the building of which he and Thibault supervised. He also executed or participated in a number of surveys, and was responsible for compiling a number of maps which demonstrate advanced cartographic techniques for the time. His maps included the following: A map of Robben Island (1785), based on a survey by C.H. Leiste*; a military map of Hout Bay and environs (1785, with Leiste); a new map showing the route followed by A.F. Beutler's* expedition to the Eastern Cape in 1752 (1786, with S.W. van de Graaff); a military map of False Bay, showing the coastline from Muizenberg to Kalk Bay (1786); a map of the Cape Peninsula on two sheets (1786, with S.W. van de Graaff); a hydrographical map of Table Bay and the adjacent coastline, on six sheets (1786); a map showing fortifications at the Cape, on four sheets (1786-1787, with S.W. van de Graaff and Thibault); a map of part of the Cape Peninsula between False Bay and Drie Koppen (1787); a trigonometrical survey of False Bay, on three sheets (1787, with S.W. van de Graaff), for which they measured a baseline of 650 toises (1267 m) on the beach east of Muizenberg; a map of False Bay showing the coastline from Cape Point to Hanklip (1787, with S.W. van de Graaff and Thibault); a beautiful 60x140 cm map of the Cape based partly on earlier sources (1787, with S.W. van de Graaff); a map of Hout Bay and the surrounding country (1787, with S.W. van de Graaff and Thibault); a map of Paarden Island, near Cape Town (1787), based on his own survey; a sketch map showing Camps Bay and Kalk Bay (now Clifton), etc. (1788); and a map of Saldanha Bay (1788) based on his own survey. Photocopies of many maps to which Barbier contributed are housed in the Cape Town Archives Repository.