NavList:
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Re: a go at Silicon Sea:Leg 81
From: Dan Hogan
Date: 2001 Oct 19, 7:31 AM
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@verimail.com Nav-L Page: http://www.wa6pby.com