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Re: SOA vs Positions
From: George Huxtable
Date: 2009 Nov 12, 23:11 -0000
From: George Huxtable
Date: 2009 Nov 12, 23:11 -0000
Thank you for clarifying, Irvin. Yes, that ship-speed did look high, but then some surface vessels can travel at that speed, so it wasn't, on the face of it, impossible without a bit of additional information, which you have just provided. Most likely, they have recorded the time of one of those observations wrong, so it covers a 2-hour interval rather than 1 hour. It provides duff data that nobody looks at, at the sending end. Very spapdash, but typical of the careless way such automated stuff gets handled. Yours, George. contact George Huxtable, at george@hux.me.uk or at +44 1865 820222 (from UK, 01865 820222) or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. ----- Original Message ----- From: "Irv Haworth"To: "Navlist" Sent: Thursday, November 12, 2009 7:52 PM Subject: [NavList 10598] Re: SOA vs Positions George H Sorry for delay in getting back to you (had wireless problem with router). I will not annoy the other members by re-hashing my past posts on ships sending WX data to WMO who appear to be using wrong term (S.O.A. ) and algorithm to calc same, run (Dist)-and/or time SOA given reported positions. In this case, given the reported positions, the correct Dist. is indeed 34.8. NM which they reported as 35 NM but S.O.A. is ( correctly ?) given as 34.8. So far so good..more or less.. except the run time is 1 hour and this cruise ship cannot attain such a speed. In earlier posts the "system"(as I have already noted) reported SOA's of over 500 kts and as high as 900 kts.(Calc based on wrong hemisphere (� W instead of E).(How is � and � determined/reviewed ?) I am simply trying to determine who or what is checking the data ...the navigator/ algorithm used or WMO ....if anybody. I have brought this matter to the attention of a US Gov chap who seems to be involved with some of these issues and while he did not have the answers ,will look into the issue and ,hopefully, advise after the 14 Nov Anno Domini 2009. Perhaps I should note here that my keen interest in these matters is that this is not hypothetical data(or supposed to be) , but is put out in real time as an additional input to WX forecasting on high seas, by W.M.O (metrological). (Garbage in garbage out appears to still be a problem ). Perhaps I should use the non de plume "fido" as one with the bone. Hi...hi Aka -Irvin -----Original Message----- From: navlist@fer3.com [mailto:navlist@fer3.com] On Behalf Of George Huxtable Sent: November-08-09 4:52 PM To: navlist@fer3.com Subject: [NavList 10509] Re: SOA vs Positions I agree with the calculation of 34.8 miles as the distance between the two given positions. What's the problem? George. contact George Huxtable, at george@hux.me.uk or at +44 1865 820222 (from UK, 01865 820222) or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. ----- Original Message ----- From: "Irv Haworth" To: "Navlist" Sent: Sunday, November 08, 2009 11:59 PM Subject: [NavList 10508] SOA vs Positions Does The plot thicken ? Dist. from 11AM/12.00 Is 34.8NM Which =34.8 Seems to indicate positions are in error ? Notes date/time lat lon naut. miles run SOA wind from knots barom. wave height air temp dew point water temp 2009-Nov-08 16:00 S 44�24' E 167�00' 43 10.7 220 27 1016.3 1.5 12.0 10.2 13.0 2009-Nov-08 12:00 S 44�24' E 166�00' 35 34.8 220 15 1019.3 0.5 12.0 2009-Nov-08 11:00 S 44�18' E 165�12' 290 15.2 250 21 1022.2 13.0 12.7 13.0 Please excuse my lead-in.it now appears the algorithm used must automatically calc. SOA based on Rhumb dist. In this case dist is 34.8 (my RL calc) and not 35 NM as NM Run. What I am trying to determine : are data generated/reported automatically from a GPS without any inputs from navigator, as well as SOA issue. ( I have been following the track of a large cruise ship across S. Pacific and now wondering what or who does what.with confidence. Reminds me of a quip in poor taste "if you drive then drink and face the traffic with confidence"). --~--~---------~--~----~------------~-------~--~----~ NavList message boards: www.fer3.com/arc Or post by email to: NavList@fer3.com To , email NavList+@fer3.com -~----------~----~----~----~------~----~------~--~---