NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Assumed positions and plots
From: Doug Royer
Date: 2004 Feb 20, 10:58 -0800
From: Doug Royer
Date: 2004 Feb 20, 10:58 -0800
Jim,I now understand what you are being taught.The course you are takeing just seems to use differant terminology than what I'm used to.On that note the following: 1.The method you are useing(being taught)is as good as the method I use.You're comfortable useing it. 2.As Fred stated, in practice, useing the method you are being taught can get the plotting sheet or chart rather messy or cluttered. 3.If you use reduction tables(H.O. 229 or 249)exclusively the AP is differant than an EP or DR.As each AP for the round of sights is differant due to each body's LHA being differant. 4.When plotting the LOPs on the sheet useing an AP(whole degree argument)try the following to reduce clutter. Instead of marking seperate dr or ep positions corresponding to each cut and plotting from such try plotting from each AP.By that I mean in the round of sights advance(or retard)each AP instead of each dr.Because the vessel's travel distance during the round won't exceed the 30' of arc tolerance between the dr and each AP it will not effect accuracy. Say you take around of 3 sights starting at 1800.The 2nd sight is at 1812 and the last is at 1823.Your course is 222* and your speed is 10 kt.The 1st AP(1800) is advanced 3.8 mi at 222* and the intercecpt and Zn are plotted from there.The 2nd AP(1812) is advanced 2 mi at 222* and plotted from there.The 3rd AP(1823) is plotted from it's whole degree position.