A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Byron Franklin
Date: 2010 Apr 20, 17:32 -0700
VISUAL NAVIGATION and the LINE of POSITION. This is for all sea men using Magnetic as well as gyro. LACK OF PROPER EMPHASIS ON LOPS ACCURACY.
The COMNAVSURFORINST 3530.4B 28 Jan 08 States and start with “While special significance must always be placed on piloting,” and continues,””Studies have shown that navigation accuracy can be adversely affected by a number of factors, including:”
b.” Lack of proper emphasis on navigation accuracy.”
C. “Improper determination of set and drift to Dead Reckoned positions.”
It continues “ about proper training. The instruction lays a good foundation but the Navy Schools and Publications teach a hindrance to both b.&c. In my apprentice as a Quartermaster striker and training, I took a bearing of a conspicuous water tank, far up the bay, trying to get a fix. My chief said “that tank never cuts in, she is plotted on the chart incorrectly.” Later in the week we were operating up the bay near to the water tank, we used it to get reasonable fixes with small triangles’ on the chart. The idea of the far tank verses the same tank when closer greatly impressed me, especially, because all publications and teaching, teach all Lines of Positions are equal, and Places the fix in the center if there is a triangle (cocked hat.) With time and experience I work my way up to the senior QM2 and chart plotter. I was able to get that good fix, finding set and drift and gave recommendation to the CONN. A new Commanding Officer came aboard, I was replaced with navigation schooled Officer, but after many replacements the new CO. reassigned me to chart plotter. The ship was a World War II Liberty hull with the original gyro and large compass errors. What made the difference, between the schooled Officers and the QM2 was my experience, I cheated on what was beening taught and in the books.
I learned that treating the LOP as equal was wrong and a hinder to accurate fixes, equally to set and drift.
I understood that the radian rule (rule of sixty) controlled each line, and a close NAVAID gave a close Line of Position to the observer while Far NAVAID gave a farther closest line of approach. How did I get that best fix possible for any given NAVAID arrangement?
I would simply select two of the closer NAVAIDS with a good sped for my fix. The third would not be part of the fix, but an indicator of accuracy. The two closes LOP. Intersection would be the best fix possible. The third told me how accurate and gave me compass error and correction.
The base to NAVAID selection, don’t do the math, but to look at the CHARTED NAVAIDS knowing that one NAVAID three times the charted distance of another closer NAVAID will have a closest point of approach CPA. Three time the distance of the closer. There are other factors of geometry that can slightly benefit the fix accuracy, but you can quickly select the best fix possible, using this simply idea will greatly improve fixes and finding a true “SET and DRIFT.” Today’s, present teaching, is Damage to accurate fixes as being taught in schools and in the publications by the Navy. This teaching is based on lack of knowledge and can be easily disproved by simple chart work.
My piloting technique has been evaluated and taught to many Officers on YP’S at OCS and Annapolis MD. In the past, these junior Officer probably never had time to use it or pass on because of all other assignments aboard ship, but it was never taught to the Quartermasters in basic school, who will do the majority of chart work aboard ship and would use it. Navy schools and publications with very large amount of personnel aretaught, all LOP’S are equal and the fix is in the center, prevents new ideas and has overwhelm a change that will improve visual navigation fixes by many yards toward the ship.
It is recommended that this technique be taught where it is most need, basic QM school.
The proof of this technique, use a chart or maneuvering board, at random, place three NAVAID with you in the center or some where on the chart. Find the true bearings to each of the NAVAIDS. Add or subtract some value (one half/ one/ or ¼ degree to the true bearings. Replot, inspect, the difference between the center of the triangle and your true position. Inspect the difference between the closes two intersections and you true position. (A large error will be more impressive 4 degrees.)
The difference may be small 20-30 yards or greater, toward the ship position and your set and drift will be the best possible, not unnessarly influenced by the farther NAVAID which is always present .
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