NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Newbie Question - Parallel LOPs
From: NavList
Date: 2009 Feb 3, 09:57 -0800
From: NavList
Date: 2009 Feb 3, 09:57 -0800
I just bought a sextant, however I am a long time land surveyor. There are a couple of things to consider when you have unexpected results. First, is from the previous comment: "the 1400 observation should be southwest". You should be able to recognize a reasonable answer from an unreasonable one even by guessing. So, always take a compass and jot down a rough azimuth of the sun. If you use a good compass and know your magnetic variation, you can check your comps for gross mistakes. And LOPs are always perpendicular to the azimuth of the sun. So, sketch it out before even calculating. Any 2 obs, 4 hours apart, spanning noon, must cross cross. Since the sun's azimuth changes some 50 degrees in 4 hours, the LOPs will cross by the same amount. A 1000 azimuth in winter is about 140 degrees. The 1400 azimuth is about 200 degrees (assuming 40 north, roughly). Keep in mind that 200 degrees of azimuth is arithmeticaly equivilent to -160 degrees (clockwise, and counterclockwise from north). That's probably the only mistake you have, 140 and -160 are 80 degrees apart, not 20 degrees. Make sense? ----------------------------------------------- [Sent from archive by: Lscott-AT-earthdata.com] --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---
