Engraving; British Library
The use of chronometers, to measure the time of a fixed location, by officers in the Royal Navy is something they were involved with on a practical level from the time John Harrison (1693-1776) submitted his first timepiece H1 to the Board in 1735. This involvement has been well documented and published, whereas the involvement with the Hydrographic Office, established in 1795, has not.
The legacy from the experiences of hydrographically orientated officers who used chronometers for navigation benefitted the Hydrographic Office, and the mariner, through the production of accurate charts. This can be traced back to men such as Captain James Cook (1728-1779), who having learned much from astronomers such as Charles Green (1735-1771) and William Wales (c.1734-1798). Dr Adrian Webb reports in this paper  that
Cook developed a superb mastery of the sextant, the chronometer, and the Nautical Almanac, and the `sheer pleasure he took in the effective use of them, inspired his successors'.
The Board of Longitude required a practical method of determining longitude at sea. Not just a one-off very expensive chronometer such as Harrisons's H4. Thus Cook took Larcum Kendall's (1721-1795) first marine timekeeper K1, on his voyage to the South Pacific from 1772 to 1775, when he found the watch to be so reliable that he described it as `our trusty friend the watch' and `our never failing guide'.