Aher, David (c.1778–1842), cartographer and civil engineer, was probably the son of Patrick Aher, a Cork surveyor; he trained under his father, in the ‘French school of [John] Rocque’ (qv). A leading Irish surveyor-cartographer, Aher was one of a new group of civil engineers, mostly of English and Scottish origin, who, equipped with superior instruments, achieved high standards of accuracy. He made noteworthy contributions to the cartography of bogs, roads, and waterways. His career began c.1796, producing estate maps for George C. Jefferyes of Co. Cork. These included the Blackwater–Shannon canal survey, praised by contemporaries as ‘most intelligent and minute’ (Cork Mercantile Chronicle, 1802, cited in Nolan & Whelan, 691, n. 19). He subsequently worked for the Grand Canal Co. (1803–5) and also carried out road surveys for Alexander Taylor (qv). From 1809 to 1813 he was employed as a surveyor on the Irish bogs commission, which proved to be a milestone in the development of Irish cartography. Aher gave valuable information to the commission, and published Queen's County and Tipperary. Maps of bogs 1811–12 (1814). In 1812 he and his junior partner and possible relative by marriage, Hill Clements (fl. 1805–24), won the grand jury contract for mapping Co. Kilkenny (completed c.1824). Possibly constructed on trigonometrical principles and pioneering in its delineation of townland boundaries, their map has been considered a masterpiece by the geographer J. H. Andrews. Aher subsequently gave evidence before a parliamentary select committee on the survey and valuation of Ireland (1824). His chief employment was as a mining engineer in the Castlecomer collieries in Co. Kilkenny, where in 1809 he successfully tapped the Jarrow seam in Glenmullen, and was the first to appreciate the characteristic qualities of Jarrow coal, particularly the absence of the usual seat of fireclay. Responding to the transport needs of the industry, he laid out several main roads through the mountainous districts to the east, north, and south, thus linking previously isolated collieries, and produced plans for the Dublin–Kilkenny railway (1832). His engineering expertise prompted the RIA to make him a member (1838).
Aher maintained a fine house, La Rive, at Big Bridge, Castlecomer, though he lived with his son Henry in Kildare St., Dublin, from 1840 until his death (5 May 1842). He was buried in Mount Jerome cemetery, Dublin. He married (1807) Susanna Wilkinson of Castlecomer; they had three sons and six daughters. Their eldest son, Henry Aher (1811–53/8), was a barrister; their second son, William Aher (1816–89), worked in Ireland, England, and also in India, where he was engineer in charge of a district on the Great Indian Peninsula Railway. Family portraits are published in S. P. Flory, Fragments of family history (1896).