| |
Latitude by Local Apparent Noon (LAN)
Time of
Meridian
Passage
The purpose of knowing ahead of time the exact time of meridian
passage (the Sun directly overhead) of the Sun is to allow the observer
and recorder to arrive on the bridge a few minutes early. A latitude line
from LAN is very useful. It is often used along with two morning
sunlines to establish a noon celestial running fix. We will again be
using a strip form to complete our sight reduction. First, we will find
the time of meridian passage, then we will work the LAN solution. For
our example problem, we will use the following data: Date: 30 March
84, DR Lat: 36°36.1'N, DR Long: 19° 22.3'W.
OPNAV 3130/35
ACTION
Completed Strip
LAN
Form
DR Long
Enter the DR longitude.
19° 22.3'W
STD Meridian
Enter the standard meridian.
15
d long (arc)
Find the difference between STD Mer and
4°
22.3'
DR Long.
d long (time)
Convert arc to time using the arc to time
+ 17 Min
page in the Nautical Almanac.
LMT Mer Pass
From the daily pages in the Nautical
1204
Almanac for the given date, enter the time
of meridian passage (bottom right of page).
ZT LAN (1st est.)
IF...
THEN...
1221
west of the
Add d long (time)
standard meridian
to LMT Mer Pass.
east of the
standard meridian
Subtract d long
(time) from LMT
Mer Pass.
Rev.DR Long
STD Meridian
d long (arc)
d long (time)
LMT Mer Pass
ZT LAN (2nd est)
Enter revised DR.
Enter the standard meridian.
Find the difference between STD Mer and
DR Long.
Convert arc to time.
Enter LMT for Mer Pass.
Add time to LMT Mer Pass.
19° 22.3'W
15
4°
40.0'
+19
1204
1223
9-36
|
