NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Plotting in True
From: Lu Abel
Date: 2009 Jul 23, 20:49 -0700
From: Lu Abel
Date: 2009 Jul 23, 20:49 -0700
There are some dreadful time sinks on the net and one of them has got to be NOAA's collection of historical charts that Frank so kindly pointed me to. I came upon a 1882 chart of Woods Hole (called Woods Holl on the chart). The chart has an annotation that says "Note: The Courses and Bearings without the Brackets are Magnetic, those within are True ..." Every single course and bearing shown on the chart is unbracketed. (They're also shown in compass points and not in degrees.) Somewhere along the line navigators were taught to plot courses in True. Plotting in True makes a lot of sense for ships equipped with gyrocompasses. But it also requires repeated TVM calculations to use an ordinary magnetic compass. Does anyone know when plotting courses in True (rather than Magnetic) became the rule?? Would I have found such a requirement in, say, an 1882 edition of Bowditch? Lu "Note: The Courses and Bearings without the Brackets are Magnetic, those within are True ..." Every single course and bearing shown on the chart is unbracketed. So there's some pretty strong historical precedent for showing courses in Magnetic!!! Lu --~--~---------~--~----~------------~-------~--~----~ NavList message boards: www.fer3.com/arc Or post by email to: NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---
