NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Peter Fogg
Date: 2006 Jun 6, 16:31 +1000
Some methods of sight reduction require use
of nearest whole degrees because only those are listed (there are other tabular
methods of sight reduction that use a DR directly).
If you are using formulas to directly
derive a result then by all means use the DR. The intercepts are likely to be
shorter, and the result more accurate for that reason. Once you have an
intercept and azimuth for each sight then plot the LOPs from the DR.
Incidentally, did you know that plotting
sheets, and all sorts of other useful stuff, are available for free from this
list’s home page:
http://www.offsoundings.info/navl.htm
Have you come across the
From:
Sent: Tuesday, 6 June 2006 4:11 PM
To:
NAVIGATION-L@LISTSERV.WEBKAHUNA.COM
Subject: Reality check
When using HO 249 The assumed latitude is rounded and the assumed
Longitude is the number that will make the LHA an even number (within the range
of +/- 30 min. of the DR Longitude). When plotting the assumed Lat and Long are
used as the starting point of the procedure. OK if I use the formulas:
Sin-1Hc = sin(dec) x sin(lat) + cos(dec) x cos(lat) x cos(LHA) and
Cos-1 (Zn)= sin(dec) - sin(lat) x sin(Hc) / cos(Hc) x cos(lat) to calculate Hc
and Z or Zn and then plot my position
wouldn't I be using the DR position as the start point?
Thank you,
Guy
