NavList:

Well since the thread from Dave Walden's question  on a fix from altitude and azimuth ran for a while I thought this maybe deserved a new thread, although I take it we now know ALL about isoazmuthal curves.

I came across this paper

Lušić, Zvonimir. "Astronomical position without observed altitude of the celestial body." The journal of navigation 71.2 (2018): 454-466. DOI

in which the idea of position fixing with just azimuth measurements is suggested, and he gives formulae for the isoazimuthal lines, and uses our favourite Napier's analogies. 

So my question is "Is there a known formula for the intersection of two isoazimuthal curves in the navigation literature"? Of course we now know this is the intersection of two quartic curves in Cartesian coordinates, or in a sereographic projection the intersection of two cubic curves. But it may be simpler than the general case.

It relates of course  Dave Walden's other post on Position from two azimuths  but digressing a little bit in to algebra. Lušić approximates with straight lines and I am sure that is reasonable on a small scale just as we do with small circles and azimuth sights.

Best wishes Bill

(ps I wonder if  Zvonimir Lušić is a member of NavList?)