Johann Christiaan Frederici (or Friderici) was recruited in Heldberg, Germany, by the Dutch East India Company as a soldier and gunsmith, and arrived at the Cape in 1784. As a soldier he rose to lieutenant of artillery in 1791, but he is best known as an accomplished surveyor and cartographer. In March 1789 he married Sophia Maria Elizabeth Bauermeister at Paarl and they had three daughters. He took the oath as a Dutch East India Company surveyor only in February 1792, after his more important work had been done.
Governor C.J. Van de Graaff* (1785-1791) did much to promote cartography at the Cape and Frederici was one of the military surveyors employed for this work. Between 1786 and 1790 he produced nine maps which formed part of the collection of maps assembled by Van de Graaff. Perhaps the most important of these was a manuscript map of the Cape south coast, based on a survey carried out in 1789-1790 by Frederici with the assistance of Bombardier Josephus Jones*. The map, which measures four by one metres and is printed on a scale of about 1:120 000, is No. 231 in the Van de Graaff collection. It depicts the coastal districts between Cape Agulhas and the eastern side of Algoa Bay, including the Langkloof, with considerable accuracy and detail. The coastline is well placed in latitude and is better represented than in earlier or other contemporary maps. The historical value of the map lies in the fact that it contains the names of many farms and farmers. It was later used by J. Barrow*, M.H.C. Lichtenstein* and W.J. Burchell* when compiling their own maps of the Cape.
Of equal accuracy, but less detailed, is Frederici's map of the west coast and coastal plain between Table Bay and St Helena Bay (No. 232). It is based partly on a survey he carried out in 1788 and parly on earlier maps, and contains later additions and notes by others. His other maps include those of Saldanha Bay, St Helena Bay and Plettenberg Bay, based on surveys he carried out in 1786, 1788, and June-July 1789 respectively; a hydrographical map of St Helena Bay showing military posts and farms (1791); and a map of the entire Cape coast from St Helena Bay to Algoa Bay (1785, with J. Jones and F.R. Duminy*). His maps are kept in the Van de Graaff Collection of the Topographical Institute at Delft, The Netherlands, while copies may be consulted in the Cape Town Archives Repository.
Frederici was also an accomplished artist and made detailed drawings of troops, ships and battle scenes. Two of his water-colours are in the Fehr Collection at Rust and Vreugd, Cape Town, while two other paintings by him are in the Mendelssohn Collection in the Library of Parliament.