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    Re: Chart-plotters, dead reckoning, pilotage, etc.
    From: Pete Solon Palmer
    Date: 2018 Sep 25, 03:27 -0400
    Hi Steve,

    <<  chart plotters -- is that they are generally not designed for usability when GNSS positioning data is not available.>>
    I agree.

    I wrote my own PC chart plotter, called NavPak to include traditional navigation tools.  It uses a vector overlay to plot bearings, celestial sights, manual entry of symbols, plus other tools for drawing text, lines, and polygons.  Also it will read Notice to Mariners and Light Lists, and plot those.

    <<  a chart plotter could be designed to accept DR inputs (heading/speed) from the operator  >>  NavPak does that using the Simulator function,  but your comment brings up an interesting idea where it could be automated. Thanks.  NavPak has all the code already in the Current Set & Drift function to collect the compass and log info, then it compares that to the GPS to get the current set and drift.  All I would need to do is expose some intermediate results to get a DR from the compass and log.  What a great idea.  It's so simple and good that it flew right over my head.

    The Simulator function will also provide GPS sentences to a RADAR (via serial cable) to keep it working in case GNSS position data is not available.

    Pete Palmer
    Global Navigation Software Co.
    Telephone: USA (619) 735-0380

    -----Original Message-----
    From: Steve Dunlop <NoReply_Dunlop@fer3.com>
    To: globenav <globenav@aol.com>
    Sent: Mon, Sep 24, 2018 8:47 pm
    Subject: [NavList] Chart-plotters, dead reckoning, pilotage, etc.

    I think that a major flaw of automated navigation systems -- chartplotters -- is that they are generally not designed for usability when GNSS positioning data is not available.  There's really not any good reason for this, because with a heading sensor and a paddlewheel log it's possible for the chartplotter to build a track using DR.  Many boats have accellerometers, which would provide another useful input.  Even absent these sensors, a chartplotter could be designed to accept DR inputs (heading/speed) from the operator, and scroll the chart continuously in accordance with the data provided.  Add radar and you could have computer-assisted pilotage near the coast, if someone were to write the code.
    Of course, fully manual DR is a skill that requires practice, as is pilotage, as is celestial navigation.  People should practice.  But then again people should floss their teeth but most people don't listen to that kind of advice.  The point here is that systems and techniques ought to degrade gracefully -- If you rely on a computer to do your GNSS navigation for you (by turning the raw coordinates into a useful navigational display) then maybe that same computer could do something of comparable utility with DR and pilotage.  I read the archives here, and people on navlist seem to like to point out that "GPS" systems are typically far more than that, true enough but they have a dependence on GPS that limits their utility otherwise.
    Too many words.  Insights welcome.
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