1st ESTIMATE OF LOCAL APPARENT NOON (LAN)
Example: Your ship's 0700 DR position on 24 January, 1981 is LAT 22° 25.0'N, LONG 46°
10.0'W. Your vessel is course 110T at a speed of 12.0 knots. What is the ZT of local apparent noon (LAN) ?
Step 1 Enter the appropriate date.
Step 2 Go to ''The Nautical Almanac" and extract the time of meridian passage for 24 January April 1981.
Step 3 Set up universal plotting sheet,Plot 0700 DR position and DR ahead to 1212 Example: 1212 - 0700 = 5h 12m at 12 knot = 62.4 miles
Step 4 Enter your DR longitude for the time of meridian passage you extracted from the almanac (1212).
Step 5 Enter the nearest standard meridian.
Step 6 Calculate the difference in arc between the standard meridian and your DR longitude.
Step 7 Convert the arc in step 5 into time using the "Conversion of Arc to Time" form the Nautical Almanac.
Step 8 Now apply the time correction to the time of meridian passage from the almanac. Because we are west of our standard meridian, we must add the difference by applying this correction you will have the time of LAN at the meridian for your DR position. This is called the first estimate of LAN:
Note: if you clocks are set to daylight savings time (DST); add one hour to your zone time or use the standard meridian that your clocks are set to.
To compute the time of LAN, I use a step by step process using this work from. After you do few problems you won't need this.
