[NicknamedBob]

"...to help calculate longitude for purposes of navigation."

Calculating longitude is one of the most difficult things to do in maritime navigation. Today we use accurate clocks and sun-sightings to know our position, when we don't want to just read it off an electronic device.

I have to wonder just how accurately one could know the longitude from the positions of major planets and star-sightings, which actually give more information than daytime sun and moon sightings. If the machine worked as I think it worked, day- and night-time readings would be set on the machine, and the output would be a navigational position in both longitude and latitude.

With the appropriate map-discs set up to display, it would be like our current dashboard location devices. The only thing hampering navigation then would be fog and rain, and lack of wind. Hence the newly realized importance of the lighthouse at Rhodes.

Need I also point out that such a device could easily show one's position anywhere on a globe, and thus one could theoretically circumnavigate Antarctica, and map its perimeter? (See the controversy regarding the Piri Reis(Sp?) Map.)

Or, in an appropriate vessel, sail to the new world?

[SunkenCiv]

I was tryin' to tiptoe around that one, just write it so others would infer it. ;') Navigation today relies a lot on GPS, as well as tried and fairly true methods. Other problems (and these are major) for earlier navigators would be reliance on natural objects (sun and moon, almost exclusively) for nighttime illumination; the need to establish an accurate circumference of the Earth (interesting that it was done pretty well in Ptolemaic Egypt by Eratosthenes, during one of the periods of brisk east-west trade); piracy (a big problem); mutiny (actually related to piracy); lack of currency standards (this would be intermittent, and as trade increased, would shrink in significance); language barriers; non-decimal number systems (math being used to calculate position and whatnot)...