That raises the question of how accurately can you measure the altitude of the Sun, an extended object, on the pitching deck of a submarine? I bet you couldn't duplicate two sightings within 10' of arc. I wouldn't be a bit surprised at an error envelope of a half degree. That would make finding longitude with a noon sight impossible.
It still seems to me the altitude of the north pole is the best way to establish latitude. If you're on land that can be done with incredible precision using a polar alignment scope. Alternately, you could use Polaris itself when the position angle of the pole is parallel with the hofizon. That happens twice a day.
The altitude of the Sun is always going to be a problem. The Sun isn't a point, its a disk. You have to find and align on the exact center of the disk.
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