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    Change of assumed position terminology
    From: David C
    Date: 2020 Apr 24, 18:56 -0700

    While reducing and plotting some sights I became confused. The results did not always make sense.  On reflection I decided that a change in terminology was needed.  I always take my sights from the same location and I have a gnss receiver. Hence the concept of a DR position is meaningless. Additionally I work sights by methods that have differing requirements for assumed longitude. I have therefore abandoned the use of the terms  "DR position"  and "assumed position" and now use three positions:

    GNSS position.  Used with the cos and haversine methods. This is the method used for checking a sextant reading.

    Assumed_t.  Longitude selected  to make the hour angle (t) a whole degree.   Latitude a whole degree.   Used with 249 and most short methods. Can also use the cos and hav methods.

                     An exception is the Aquino method. The table lookup begins with t a whole degree. It is not necessary to calcuate the corresponding longitude.

                     The  Aquino table provides an assumed longitude (for which t is not a whole degree).

    Assumed_p.  Lat and long  selected to make plotting easier - typically whole degrees. Used with the cos and laversine methods.

                    As an example I am at long 175° 05.2'. An obvious value for long_p is 175°.

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