I looked up the history of the rangefinder and the work of Watt in the 1770s is kind of obscure. For one, he called it a “micrometer” [0] even though he also cr

I looked up the history of the rangefinder and the work of Watt in the 1770s is kind of obscure. For one, he called it a “micrometer” [0] even though he also created something like what is called a micrometer today, only he called it an “end measuring machine.” Additional confusion comes from “telemeter” as an early term for a rangefinder. Only Watt was also there at the beginning of what we now call telemetry: “additions to his steam engines for monitoring from a (near) distance such as the mercury pressure gauge and the fly-ball governor.” [2] Watt's micrometer, designed between 1770 and 1771, was what we would now call a 'rangefinder'. It was used for measuring distances, and was essential for his canal surveying work. Adapted from a telescope, with adjustable cross-hairs in the eye-piece, it was particularly useful for measuring distances between hills or across water. 0. https://digital.nls.uk/scientists/biographies/james-watt/discoveries.html https://digital.nls.uk/scientists/biographies/james-watt/dis... 1. https://collection.sciencemuseumgroup.org.uk/objects/co59281/watts-end-measuring-machine-micrometer https://collection.sciencemuseumgroup.org.uk/objects/co59281... 2. https://en.wikipedia.org/wiki/Telemetry https://en.wikipedia.org/wiki/Telemetry