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    Correct way to draw LOPs
    From: Rick Emerson
    Date: 1999 Jun 22, 07:26 EDT

    Russell Sher writes:
     > Hi - is the corect way to draw an LOP a line with a arrowhead at each end?
     > Or is it a single arrowhead pointing to the bearing of the object.
     > Russell
    An LOP is perpendicular to the bearing so drawing an arrow pointing
    to the bearing isn't a hot idea.  Typically, a straight LOP can be
    drawn with an arrow at either end: <---------->  while an advanced LOP
    is drawn thus: <<---------->> The double arrows indicate the LOP is
    advanced from an earlier LOP.  Mark the initial LOP with time and date
    (if the LOP is a celestial LOP, I add the appropriate symbol for the
    body used to obtain the LOP) and mark both the initial and later time
    stamps on the advanced LOP.  The idea is to be able to determine what
    data lead to the LOP's; some days it's useful to figure out where
    (horrors!) an error came from.
    The distinction about straight LOP's is made because there are also
    arc LOP's based on range from a point where the bearing is uncertain.
    A LORAN fix, for example, is really three intersecting arc (well,
    hyperbolic) LOP's where range is based on time delays.  Other examples
    include radar ranges and ranges determined by measuring the angle
    between the horizon and top of an object of known height (e.g.,
    S/V One With The Wind, Baba 35

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