Navigation in the Modern World

Along the garden path and up the stairs

Prior to the theodolite, instruments such as the groma, geometric square and the dioptra, and various other graduated circles (see circumferentor) and semicircles (see graphometer) were used to obtain either vertical or horizontal angle measurements. Over time their functions were combined into a single instrument that could measure both angles simultaneously.

The first occurrence of the word "theodolite" is found in the surveying textbook A geometric practice named Pantometria (1571) by Leonard Digges.[3] The origin of the word is unknown. The first part of the Neo-Latin theo-delitus might stem from the Greek θεᾶσθαι, "to behold or look attentively upon"[4] The second part is often attributed to an unscholarly variation of the Greek word: δῆλος, meaning "evident" or "clear".[5][6] Other Neo-Latin or Greek derivations have been suggested as well as an English origin from "the alidade".[7]

The early forerunners of the theodolite were sometimes azimuth instruments for measuring horizontal angles, while others had an altazimuth mount for measuring horizontal and vertical angles. Gregorius Reisch illustrated an altazimuth instrument in the appendix of his 1512 book Margarita Philosophica.[3] Martin Waldseemüller, a topographer and cartographer made the device in that year[8] calling it the polimetrum.[9] In Digges's book of 1571, the term "theodolite" was applied to an instrument for measuring horizontal angles only, but he also described an instrument that measured both altitude and azimuth which he called a topographicall instrument [sic].[10] Possibly the first instrument approximating to a true theodolite was the built by Josua Habemel in 1576, complete with compass and tripod.[8] The 1728 Cyclopaedia compares "graphometer" to "half-theodolite".[11] As late as the 19th century, the instrument for measuring horizontal angles only was called a simple theodolite and the altazimuth instrument, the plain theodolite.[12]

The first instrument to combine the essential features of the modern theodolite was built in 1725 by Jonathan Sisson.[12] This instrument had an altazimuth mount with a sighting telescope. The base plate had spirit levels, compass and adjusting screws. The circles were read with a vernier scale.

  • Jesse Ramsden's Great Theodolite of 1787's Great Theodolite of 1787
    Jesse Ramsden's Great Theodolite of 1787
  • A theodolite of 1851, showing the open construction, and the altitude and azimuth scales which are read directly
    A theodolite of 1851, showing the open construction, and the altitude and azimuth scales whic
but a theodolite isn't a navigation tool, it's a measurement tool.
North star.

I was told it was how my ancestors navigated home.

Be home any minute now. Wish I had brought a wet suit.

Perhaps they should consider a firmware upgrade

View attachment 756111
Useless, only works half the time.
 
Im looking at Komoot, think it might serve my needs quite well
Looks like a nice app

On a more serious note I don't use navigation most of the time unless inner city. I just follow signs. Inner city I need it and I find a smartphone sufficient. When I'm in the sticks I usually just keep going until I see a road sign with a familiar town name and head towards that.
 

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