Gustav A. Troye, surveyor, cartographer and consulting engineer, was educated in Germany and at the Camborne School of Mines in Cornwall. He emigrated to the Cape Colony in 1877, at the age of 17, and fought as a volunteer in the Gaika-Gcaleka War (Ninth Frontier War) of 1877-1878 and the Anglo-Zulu War of 1879. In 1882 he settled in the South African Republic (Transvaal) and during 1884-1889 worked in the surveyor-general's office in Pretoria. In 1886 he married Amy Gooch, with whom he had four children. He moved to Johannesburg in 1889.
Troye compiled a number of important maps of the Transvaal and its gold fields. His Map of the Pretoria and Heidelberg goldfields (1600 Cape roods to the inch, or c. 1:238 000), dated February 1887, was published in London. It was followed a month later by his Map of the De Kaap and Komatie goldfields, and all adjoining goldbearing properties (3.5 miles to the inch, or c. 1:222 000), which gave an accurate picture of mining activities in the Barberton area. Troye's map of the Witwatersrand goldfields (600 Cape roods to the inch, or c. 1:89 000), compiled in Johannesburg in 1889, was the first detailed map of the Witwatersrand and included a geological section from Pretoria to Johannesburg and Roodepoort. However, his most important contribution to cartography was Troye's map of the Transvaal or S.A. Republic (1:500 000, on 6 sheets), lithographed in Switzerland and published in six colours in Pretoria. It was the first topo-cadastral map of the Transvaal and by far the most complete, accurate and attractive map of the territory produced up to that time. He used farm diagrams and inspectors' records in the surveyor-general's office to map farm boundaries and list farm names, while information was also obtained from F.H. Jeppe's* map of 1889 and supplied by R.K. Loveday* and others. This map probably formed the basis of Troye's new map of the Transvaal Colony (2000 Cape roods to the inch, or c. 1:297 000), compiled about 1902 by L.M. Boddam* and G.A. Troye. This topographic, cadastral and geological map was the first complete geological map of the Transvaal. On it the Bushveld Igneous Complex is correlated with the Cape Supergroup, both of which are regarded as of Devonian age. The map was compiled by Boddam, while its geological information was revised and edited by Troye.
From 1892 to 1896 Troye was in charge of the Mines Survey Department of the Barnato Group (JCI). His work there provided the background for his "Notes on mine surveying, with special reference to the Transvaal", published in the Transactions of the Institution of Mining and Metallurgy for 1900-1901. During 1897 and 1898 he travelled in Australasia and North America, visiting the pricipal mines in these regions. After the Anglo-Boer War (1899-1902) he was a consulting engineer in Johannesburg until 1913 and for some time served on the Johannesburg town council. In 1913 he retired to his farm Amatava in the Waterberg, to develop citrus orchards and breed thoroughbred Catalonian donkeys and cattle. However, in 1923 he published A paper on an important source of petroleum, motor spirit, lubricating oil, and paraffin wax in South Africa (Johannesburg, 7p), dealing with occurrences of the mineral torbanite (oil shale) in the Transvaal. The Johannesburg suburb of Troyeville, which he surveyed, was named after him, as was Troye Street. He was a member of the (British) Institution of Mining and Metallurgy, and a Fellow of the Chemical Society.