One of the possible uses of sundials is to help navigation on land. The armies of several countries as well as various scientific expeditions have used instruments derived from the sundial for navigation in desert regions.

In 1701, the mathematician, Antoine Parent, described in a paper addressed to the Academy of Sciences the possibility of constructing a universal instrument for measuring time based on the analemmatic sundial. In practice, it only partially deserved the title “universal“ since its use in northern latitudes was rendered impossible on account of its cumbersome dimensions. This dial had every chance of being forgotten, precisely because of its universal nature. Only a limitation of its latitude range made it re-appear.

In 1920, we find the same type of dial, described in a USGS (United States Geologic Survey) bulletin. This device, Baldwin's sun graph, was used for direction finding. It was also a multi-latitude analemmatic dial (covering latitudes from 30 degrees to 70 degrees) but which differed from Parent's in that the latitude ellipses all have the same major axis. In order to position the gnomon correctly for a given date and latitude, it is necessary to use a special graph built into the dial plate. It seems that Parent's dial is easier to use and it is doubtless for this reason that twenty years later someone decided to use this somewhat forgotten man's dial.

A sun compass used by British army in north Africa.
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The astro compass was a navigation instrument used in bombers.
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