NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Silicon Sea: Leg 82
From: Brian Whatcott
Date: 2001 Dec 02, 6:09 PM
From: Brian Whatcott
Date: 2001 Dec 02, 6:09 PM
Anybody care to help a beginner? I would like to get up to speed from a basis of pilot navigation - which doesn't use identical jargon. Unfortunately, that means asking about just about every term used in the problem. If this is too much - tell me - and I'll understand. For example - mag var is the difference beween true north and the direction in which a perfect compass may be expected to point - OK: but deviation: is this the error in a compass reading due to stray fields remaining after correction, and shown on a compass correction table? Current speed and set: is this a vector like wind speed and direction? Wind direction is the direction from which the wind blows: Set, is this the direction towards which the current moves? Is it always given as a magnetic direction? Is compass course the compass track between present position and destination? What does LL mean, in the "sun LL" context. What does Hs mean? What does Zn mean? What is the RFIX (referred fix??) HE is head elevation? Index error is a sextant correct? how found?? Sailings? Affect?? What do I use for charts and plotting - where do I get them? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`` Thanks in advance Brian Whatcott At 03:51 PM 12/2/01, you wrote: >Chart(s): Plotting Sheets > >Sight Reduction and >Dead-Reckoning problem Leg 82 120101 Test your knowledge! >---------------------- ------ ------ -------------------- > >Our last position FIX was (11d 29.8'N 132d 29.5'W) 11/07/2001 @ 03:40:15UT. >We are bound for a landfall at Hawaii(19d 30.0'N 154d 45.0'W). Var 10.0dE >Dev 1.0dE; Current Drift 0.7 Kts Set 285d. Speed 9.7 Kts. > >1) What is the Compass Course(CC)/Course-to-Steer for our Hawaiian > landfall point? >-- --------------------------------------------------------------- > >2) Based on the available information, what is the anticipated > Speed Made Good(SMG) to the Hawaii waypoint? >-- ----------------------------------------------------------- > >The sky has been overcast for days. we have been unable to get a sight. >Var 10.0dE Dev 1.0dE. Speed 10.4 Kts. > >Since the last FIX(11d 29.8'N 132d 29.5'W) 11/07/2001 @ 03:40:15UT, >navigating only on dead-reckoning having sailed a total of 1170.0 Nmi. >We take a SUN LL sight: > > DATE UT/GMT Hs > > 15/07/2001 20:10:35 61d 20.6' > >3) What is the DR position? >-- ------------------------ > >4) What is the Speed Made Good(SMG) to this DR? > What is the Compass Course(CCMG) this DR? >-- --------------------------------------------------- > >At 01:44:36UT that same day we take another SUN LL sight. Use your plotted >True Course(TC) and Speed 10.2 Kts: > > Hs 40d 44.1' > >5) What is the Zn bearing of the SUN at the above sight? >-- ----------------------------------------------------- > >6) What is the RFIX position? >-- ------------------------- > >7) From our DR position, what is the Distance Off and True direction of > the Running FIX? >-- -------------------------------------------------------------------- > >8) What is the TC and Distance to the Hawaii landfall point at > (19d 30.0'N 154d 45.0'W) from the FIX?: > > You should try at least two of the methods. > > On a Great Circle? > On a Rhumb Line? > On Mid-Latitude Sailing? > On Mercator Sailing? >-- ----------------------------------------------------------- > >8a) As an aside try calculating from the RFIX to Sydney > (33d 50.0'S 151d 20.0'E). >-- --------------------------------------------------- > >NOTE: >Lat & Lo = XXd XX.X', Date=DD/MM/YY, HE 9 Feet, Index correction >-2.5', Time hh:mm:ss in UT,unless otherwise stated. Silicon >Sea II is a 34,000 lb(15.40t) displacement sailing vessel, 48' 3" >(14.70m) LOA. 39' (12.00m) LWL; Cutter rigged. Can tack to 45d. >Water Tanks = 220 gal(1000 ltrs). Fuel Tanks = 155 gal(700 ltrs). >Fuel consumption .675 gal/Hr at 8.5 Kts. DR(Dead-Reckoning)=position >by sailings, EP(Estimated Position)=DR+current affect. Dist to >Horizon: Nmi = SQRT HE@mtrs x 2.07; Nmi = SQRT HE@ft x 1.17. > >PLEASE respond with your results and thinking on these exercises to >the NAVIGATION list at large. If you have questions or problems, A >lot of folks on the list are knowledgeable and willing to help. Any >questions or doubtful areas will be responded to promptly. Let us >hear from you soon! > >Good Navigating! > > -=The Navigation List Working Group=- > > Peter Smith - Smith_Peter@EMC.COM > John Simmonds - johnsimmo@dingoblue.net.au > Tony Cappiello - cappiello@kearfott.com > Frank Norris - NORRIS_FRANKLIN_H@LILLY.COM > Sam Chan - schan@socal.rr.com > Mike Wescott - wescott_mike@EMC.COM > Dan Hogan - dhhogan@veriomail.com > >*****************************ANSWERS LEG 82******************************* > >1) CC= 279.7d > >2) SMG= 10.4 Kts > >3) DR= 18d 17.6'N 151d 17.8'W > >4) SMG= 10.8 Kts > CCMG= 280.3d > >5) Zn= 282.5d > >6) RFIX= 18d 37.2'N 152d 13.6'W > >7) DistOff= .2 Nmi > Direction= 187.7d > >8) GC= Init. > Course= 290.7d > Dist= 152.5 Nmi > RhumbLine > Course= 290.1d > Dist= 153.3 Nmi > Mid-Latitude > Course= 290.3d > Dist= 152.5 Nmi > Mercator > Course= 290.1d > Dist= 153.4 Nmi > > >Dan Hogan WA6PBY >C27 "Gacha" >dhhogan@verimail.com >Nav-L Page: http://www.wa6pby.com Brian Whatcott Altus OK Eureka!
