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How to Convert Arc to Time Using The Nautical Almanac
Example
In the following example, you will learn how to convert arc to time using
a table from The Nautical Almanac.
Example: Suppose your DR longitude is 142° 41' W, and ZT is 06h 21m
09s. Divide 142° 41' by 15, and you find that your ZD is +10. This
means that your standard meridian must be 150°W. To simplify the
arithmetic, express the 150°W longitude as 149° 60' W. The values are
equal and subtraction is made easier this way.
Standard time meridian
149°60' W
Longitude your meridian
142°41'
Difference of Longitude
7°19'
Using the conversion of arc to time excerpt shown in figure 5-4, change
7° 19' to time, and you get 00h 29m 16s. This means that LMT at your
meridian differs from ZT by 00h 29m 16s.
Figure 5-4. Excerpt from The Nautical Almanac.
5-10
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