DEAD RECKONING FIX OF ESTIMATED POSITION ALONG LOP
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When only one line of position (LOP) is available, it is possible to find your estimated position (EP) by using the dead reckoning position (DRP) as a guide. Spreadsheet dr_fix_lop.xls finds the EP as the point along the LOP which is closest to the DRP. The previous known position is entered in cells A3 and B3, average speed in knots in cell A7, time interval in hours in cell B7 (formatted as a regular floating point number), and course in cell C7. The LOP is defined as usual by the GP and Ho (cells D3, E3, and F3). The EP is displayed in row 11. The distance (in nautical miles) and bearing from the DRP to the EP are shown in cells C13 and F13, respectively.
Summary for spreadsheet dr_fix_lop.xls:
Input cells: A3, B3, D3, E3, F3, A7, B7, C7
Output cells: A11, B11, C11, D11, E11, F11, C13, F13
The problem preset in this spreadsheet is a variation on the one treated in The Celestial Navigation Mystery Solved by David Owen Bell on p. xliii (Problem 1).
The auxiliary mini spreadsheet time.xls can be used to add and subtract time data and also to perform conversions between the HH:MM:SS and hours-decimal formats.
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