Join Date: Jun 2002
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Check my Plotting...
I guess this exchange illustrates the importance of using your eyes, instead of half-remembered rules, sliderules, and gadgets. I''ve never gotten the var/dev thing wrong with a compass rose in front of me, but I''ve never remembered the memory tricks I''ve learned a hundred times.
More to the point in my view is the implication in your original question that such a precise course could ever be steered, or even drawn onto your DR plot. Not even the most attentive autopilot can steer within a degree of a designated course, outside the tranquility of a windless harbor morning. Unless you''re planning to drive tankers, calculating to such a degree of precision is wasted, and masks the need to view the DR with the skepticism that it''s inherent inaccuracy deserves.
Plot it accurately, within reason, but use it as a reality check against your fixes, or as a record of where you ought to be should fixes become unobtainable. Don''t try to put yourself on top of Diamond Head buoy after crossing the Pacifc with just your compass and DR, though!