NavList:

In a previous post, the practical nature of approaching a destination via a latitude line was considered.

This is my understanding.

Let us assume that the destination is precisely at N40 deg 0 min of latitude. The clever navigator will choose a latitude line just to one side of this for the following basic reason. If you sail on precisely N40 deg 0 min (or so you think, because you have been using DR for days) what happens when you hit land and the destination is not in sight. Is the actual destination to the north of you OR to the south? This is an unresolvable uncertainty. You may as well flip a coin.

By sailing to one side of the destination latitude, say N40 deg 15 min, when land is sighted, you KNOW that you must turn to the south and sail for a few miles until the destination is observed. No need to investigate the northerly coast, the destination is clearly to the south by design.

In modern day GPS navigation, you sail directly towards the destination because there is no uncertainty, and the only DR performed is when you aren't observing the GPS. But of course, this is a celestial navigation group, so we cannot use principles of GPS navigation.

Brad
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