A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David Pike
Date: 2015 Nov 26, 12:18 -0800
If waypoint A is lat 60N 000E/W and you travel 60nm in a direction 060°.
Increase in latitude (northing) = 60nm x Cosine 60° = 60 x 0.5 = 30nm. Therefore, latitude of B = 60° 30’N
Distance travelled east (easting) = 60nm x Sine 60° = 60 x 0.866 = 52nm.
Change easting into minutes of longitude = 52 x Secant 60° = 52 x 2 = 104’ east
Therefore, lat and long of B = 60° 30’N 001° 44’E.
I bet even a dunce like me could turn that into an Excel spreadsheet, but I’m not going to. I’ll leave that up to you. Look after the degrees and the signs (and sines) will look after themselves. E.g. enter 'cosine 240° ' on a calculator, and it'll come up minus automatico. That explains why with some mapping applications on the Internet longitudes don't come up in E & W; they come up in + and minus. DaveP
I said I wasn’t going to try putting my short distance waypoint calculation into Excel, but I couldn’t resist it. I’ve got it working below in decimals of degrees apart from crossing 180E/W. However, I’ve failed in turning this back into degrees and minutes because INT always makes negative numbers more negative. E.g. 3.5 degrees west or south, i.e. -3.5 degrees, comes up as -4 degrees + 30’. Can anyone make lines 18 and 33 more useable? DaveP