A pantograph is an instrument that has moveable parts that enables copying through the use of replicative mechanical movements at varying scales (more: Map Scale). Before the use of computers to replicate and manipulate maps, a pantograph was one of the ways used to either reduce or enlarge the size of a map while reproducing an accurate copy of the original map.
The word pantograph is a concatenation of the Greek word, pan, meaning “all” and graph for “write”. The use of the word pantograph itself originated from the French word pantographice whichwhich was introduced in the French lexicon in 1631. Per the Oxford English Dictionary, the English word debuted in 1723 (in E. Stone tr. N. Bion Constr. & Principal Uses Math. Instruments 86).
The pantograph itself was invented by Christopher Steiner, a Jesuit priest from Germany, sometime between 1603 and 1605. Steiner created the pantograph as a way of copying plans at different scales. Steiner didn’t document his invention until he published “Pantographice seu Ars delineandi res quaslibet per parallelogrammum lineare seu cavum” in 1631.
The pantograph works by connecting one arm of the pantograph to a pointer and another section of the pantograph contains a drawing implement. Scale is increased or decreased by adjusting the arms and thereby the relationship of the linkage between the pointer and the drawing implement.
This article from Southwest Builder and Contractor published on January 26, 1934 shows engineers using a very large pantograph to create an accurate reduction of tunnel contours.
This video demonstrates how a pantograph is used to create a smaller or larger copy of a picture: