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Great-Circle Vertex

Highest-latitude point (vertex) of a great-circle track - where the track runs true east-west. Napier's Rules of circular parts.

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Formula, assumptions, and limits

cosLV=cosLsinC\cos L_V = |\cos L \cdot \sin C|
SymbolMeaningUnit
LLAny known latitude on the track°
CCInitial course at that point°T
LVL_VVertex (highest) latitude°

Source: Bowditch - American Practical Navigator Ch.24

In short

Highest-latitude point (vertex) of a great-circle track - where the track runs true east-west.

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