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    Re: Susceptibility of GPS to CME, Rationale for CN?
    From: Brad Morris
    Date: 2018 Oct 1, 18:50 -0400
    Hello Kermit

    You wrote:  CelNav / DR has been, is and will remain a worldwide Oceanic Navigation System.  It will remain a back up one...

    Kermit,  I have deep respect for your attention to detail and understanding of CN.  I try to understand what you are doing,  so that I may learn.  However, that statement, in my opinion, is illogical.  CN cannot be a backup in the sense that you will need it when there is no GPS.  I have struggled these past few weeks to find the rationale to make it a backup.   

    The consensus is that CN is NOT  a backup for GNSS.  We cannot find a rational, reasonable circumstance under which the GNSS (and others like GLONASS) system goes down pushing the navigator into a CN regime.

    There are some narrow circumstances of course:
    1) War among US, China & Russia.  Each has demonstrated capability to attack satellites.  The parties must remove all navigational satellites from orbit.
    2) Carrington level solar event or greater, possibly destroying satellites and receivers.
    3) Denial of service by interference in the command and control architecture to the satellites.
    4) Lightning strike, which fries every bit of electronics on the vessel.  Requires that backup GPS receivers not be properly stowed and are also damaged by the same strike.
    5) Spoofing and jamming.

    If you, Kermit, wish to call CN a backup to GPS, please do identify the circumstance that forces your hand into the CN regime.  I encourage you to do so, very strongly so!  Please!  Otherwise, CN isnt a backup.  Full stop.

    In discussion of the narrow cases listed above, the probability of occurence remains quite low.  For example, vessels are struck all the time by lightning and that lightning can and will fry electronics.  All of the battery powered GPS receivers must also be damaged, simultaneously.  If only one GPS receivers, of many, survives, CN still won't be used.  Sure, that could happen but it's a fairly rare combination of events.

    The consensus re CN is that we do it because CN is fun and it exercises the mind.  When forced to show how CN is a backup to GPS, the circumstance is so improbable as to negate the circumstance.

    Again, I have nothing but great respect for your capabilities.  

    The backup to a failed GPS receiver is another GPS receiver.  Change my mind.


    On Mon, Oct 1, 2018, 1:24 PM Antoine Couëtte <NoReply_Couette@fer3.com> wrote:

    Hello guys, let's us make it easy to this point.

    When we have no Long Range Maritime Oceanic Navigation left but CelNav we will be quite happy with only CelNav left, very happy indeed, all agree ?

    A number of ourselves as well as our Forebears have experienced this environment for centuries in the past.

    May this situation - i.e. nothing left but CelNav - happen in any foreseeable future ? Nobody can 100% rule it out.

    CelNav has defects as we all agree, but it has nowadays the extra advantage that we can tackle it so much easily with the computation power at our fingertips. It has almost become fun.

    CelNav / DR has been, is and will remain a worldwide Oceanic Navigation System.

    It will remain a back up one, if not the last resort one.

    In other words: "La messe est ditte, allons diner" *** says it all.

    ***  Meaning: "The Mass is ended, let's have dinner" from the sentence on the last page of the Organ "Mass for the Parishes" manuscript (1698) by François Couperin Le Grand.

    Antoine M. "Kermit" Couëtte


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