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    Wartime (WW2) navigation
    From: Trevor Bell
    Date: 2010 Jan 31, 08:32 -0800

    Thanks to everybody for your responses to my original post. Everybody wants more detail so here goes:

    Rangitane left Auckland for Panama under the direction of the naval control service (NCS). After passing Curvier light (36d 25m S,175d 47m E) the first waypoint was to be 38d 00m S, 15d 00m W, the next 32d 00m S, 130d 00m W before heading for Los Santos point 7d 30m N, 80d 00m W.

    Rangitane was sunk (recorded by three sources) at 36d 58m S,175d 22m W - an estimated position under prevailing conditions. The captain had been instructed by NCS to take a great circle track between the waypoints. By my simple calculations this puts the sinking almost exactly 50nm north of the nearest great circle path to the first waypoint. Had Rangitane sailed a direct great circle route to Panama (not via waypoints) she would have been sunk about 38nm south of that route.

    My question about sailing great circle or rhumbline is pertinent because, under interrogation at a subsequent enquiry, the Rangitane captain said that they might have sailed a Mercator route to the first waypoint, not great circle as required by NCS. If so, were the sinking coordinates on such a rhumbline - and, in the absence of charts, this is where I am struggling for a calculation.

    The underlying question is - did the Germans find Rangitane by design or by chance? Rangitane would have been sailing on a heading of about 090 while the Germans were sailing on about 010 - from ship logs they were definitely not shadowing her. If the Germans had been told Rangitane's departure time, course and waypoint, how come they intercepted her so far off course in total darkness? From other expert advice I have already discounted the possibility of radio direction finding.

    Thanks glapook for the attachments - I will have a go at the tables and thanks to everybody else for comments and links. There is clearly a wealth of information out there!

    Trevor Bell

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