NavList:

Bruce,

There are two ways which I use to advance lines of position.

1. Advance the assumed position along the vessel heading using time, speed and distance tables or a pocket calculator. From the advance A.P. plot the azimuth and intercept.

2. Advance the line of position from the course track intersection along the track line to the desired DR position.

Greg Rudzinski

[NavList] Advance LOP of High Speed Vessel
From: Bruce J. Pennino
Date: 8 Nov 2012 21:12

Hello:

I've followed the Trans-Atlantic postings closely. Thank you Kevin and all those working on the CN/ sight data. I realize I don't understand the most correct technique to advance the first LOP on a Universal Plotting Sheet based on DR.

For example, for a vessel at 17 knots with the first LOP @ about 49 Deg N, and 3 hours between sights, the first LOP must be advanced in parallel fashion 51 NM . If vessel is going true N or S, LOP moves N or S 51 minutes of arc.

If going true E or W, we know 51 NM is about 77 minutes of arc (at 49 N there is about 39.5 NM/degree of longitude). For DR we plot the new DR ---

For all other courses, change x and y scales to NM and use vectors? Linear or trig approximation? I just don't seem to find the answer exactly in any of my three CN books. The proper technique is probably there, but I'm not seeing it!

Thanks in advance.
Bruce

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