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    Re: a go at Silicon Sea:Leg 81
    From: Dan Hogan
    Date: 2001 Oct 19, 7:31 AM

    On 19 Oct 2001, at 16:01, Peter wrote:
    1)  What is the current DR position?    N10d 20'.5   W128d 37'.6
    
    OK
    2)  What is the approximate distance and direction to the storm 822nm at 045d
    TC
           (019d 45.0'W  120d 30.0'N - am assuming lat. and long. simply
    transposed here)
    The intent was to ask for the direction and TC to the storm.
    
                                                      from N10d 20'.5  W128d
    37'.6 at 14:00:00 UT on 06/07/2001
        6 Hrs       289.9d      9.5Kts                   N10d 40'     W129d
    32'    at 20:00:00 UT on 06/07/2001
        12 Hrs      278.0d      6.2Kts                 N10d 50.4    W130d
    46'.9    08:00:00 UT      07/07/2001
        5.5 Hrs     275.0d      4.5Kts                 N10d 52'.6   W131d
    11'.9    13:30:00 UT      07/07/2001
        36 Hrs      270.0d      Hove-To fore reaching at 1.3Kts
       Am assuming 270d TC is direction boat is forereaching - incidentally,
    while the boat is doing this it is not hove to. It's an important point,
    while the boat is stationary it will slowly fall away to leeward, thus
    leaving relatively calm water to windward. While it is forereaching it is
    constantly moving out of this calmed water. This can make all the difference
    between being able to remain hove to and needing to make other plans.
    
    3)  What is the DR position at the end of this time?  N10d52'.6   W131d 59'.5
    OK
    4)  What is the UT/GMT date and Time?                        01:30:00 UT on
    09/07/2001
        What is the Zone Time(ZT) and day?    zone W9    16:30:00 ZT on
    08/07/2001
    OK
    5)  What is the TC & Distance from the DR to our Hawaii landfall point at
        (19d 30.0'N  154d 45.0'W)
    Approx. 1400nm at 292d TC (I'll have to find a way to work this out
    accurately - any clues?)
    
    6)  What is the unknown body?     Vega, with a magnitude of 0.1
    
    OK
    7)  What is the FIX position at the time of the unknown body?
    Fix at 18.40 ZT  N11d 29'  W132d 28'.9
    
    Hmmm. Check the Latitude.
    One problem I've come across before, with SS:leg 80, for example, is that if
    my calculations for one step do not agree with yours, then further
    calculations using this data cannot help but become more and more different,
    if not wrong. But even if my DR seems dodgy, am happy to see that these
    sights form a neat tight plot; errors - distance from fix point to position
    line - are as follows
    Vega     Az 052.1 Int A  0.8    Err +0.5
    Mars          133.6      A45.2           -0.7
    Antares      139.3      A47             +0.7
    Regulus      277.6     T32.6           +0.7
    Dubhe        336.3     T45.3           -0.4
    Rasalhague 082.7      A24             +0.1
    Silicon Sea problems are calculated using Navig94 for the answers. Using
    different systems/methods will produce slighty different answers. But as an
    old sea Captain said, Putting his palm on the chart, "We are some place in
    the area."
    
    Dan Hogan WA6PBY
    C27 "Gacha"
    dhhogan{at}verimail.com
    Nav-L Page: http://www.wa6pby.com
    

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