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(05-04-2018, 06:49 PM)iancampbell Wrote: Indeed. The problem with that, in this scenario, is that longitude measurement by comparing local time to GMT only works if you have a chronometer set to GMT in the first place - which, in this scenario, you don't.
You can set it arbitrarily to local sunrise so that as you travel and explore you have a reference point for the longitude based on your start. If the goal is to be exact about current longitude lines then it wont work (unless in the process of your travelling you find and can identify the exact GMT line) but it will be very helpful for basic navigation.
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(05-04-2018, 11:43 PM)Rynn Wrote: (05-04-2018, 06:49 PM)iancampbell Wrote: Indeed. The problem with that, in this scenario, is that longitude measurement by comparing local time to GMT only works if you have a chronometer set to GMT in the first place - which, in this scenario, you don't.
You can set it arbitrarily to local sunrise so that as you travel and explore you have a reference point for the longitude based on your start. If the goal is to be exact about current longitude lines then it wont work (unless in the process of your travelling you find and can identify the exact GMT line) but it will be very helpful for basic navigation.
Precisely. In a situation like this, you set an arbitrary zero of longitude. Probably at a clear and reasonably permanent landmark near where you arrive.
That's how the real-world longitude zero was set, after all. It's also how we have set at least one other longitude zero; the one I'm thinking of is the one on Mars. It's set as the position of a particular small crater that's easy to find from orbit.
Ditto the Moon, although in this case it was chosen because the relevant crater is near the centre of the lunar disc as seen from Earth.
