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I am also not sure why did they use another projecton.
The article in the American Math Monthly (mentioned on the list
in this same thread) describes in detail
the principle of the work of the device, but it does not mention
that a similar but simpler device is known for more than 2000 years.

On the other hand, the article says that the new device was tested
in airplane navigation, has accuracy "few minutes" (!) and
has size 11 times 12 inches.

All this taken together is hard to believe, unless
"few minutes" really means 20 minutes:-)

Alex.




>> I was talking of the stereographic projection (where one only needs
> to draw circles)
>
> It is same kind of device with almost identical purpose and use and it
> should look very similar. The only difference is that in the pictured
> device they use azimuthal equidistant projection of grid of parallels and
> meridians instead of traditional stereographic.
> I can only guess at their reasons for doing so. One thing is that in
> stereographic projection distance betwen parallels grows as we get further
> from the center. For example distance between 80 and 90 is about twice the
> distance between 0 and 10. Azimuthal equidistant avoids this feature
> (that's what "equidistant" in the name means).
>
>
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