A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Position-Finding
From: David C
Date: 2017 Dec 1, 17:42 -0800
I live approximately 31km NE of Wellington Airport so this may be a trivial excercise. I opened the geo-aching app on my phone and entered the given coordinates of Boston. To locate a cache in Boston I will need to travel 14664km (7918nm) with an intial heading of 65°. Mentally 65° seems about right.
But the question was about travelling from Boston to Wellington. I opened my trusty copy of Nories tables to determine thehalf-convergency. This will allow me to calculate the Wellington - Boston loxodrome and by simple subtraction the Boston - Wellington value. Reapplying the half-convergency gives the initial GC bearing from Boston.
Mean lat approx 0°
dlong approx 115°
so from Norie the half-convergency is < 1°
The latter should have been obvious to me without consulting Norie. Boston and Wellington are at similar (but opposite) latitudes so the difference between a GC and a loxodrome is very small. Flight planning therefore is very simple. Follow the 295° loxodrome from Boston. The simplest way to arrive is to home on the 100kw AM station 2YA on 547 kc/s ( oops khz) which is almost on the final approach for runway 16, about 30km north of the airport. A bonus is that 2YA is a great station to listen to - I have it on in the background.
PS Please do not attempt this fully loaded from South to North as the runway end may be reached before takeoff.