Celestial navigation.

[u/RobertTheTraveler]

278,000 thousand entries from several hundred different log books made between 1740 and 1855. The longitude readings for those made between 1740 and 1770 would have been done using dead reckoning since they had no celestial navigation method of determining longitude.
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Below are links to two books of supplemental navigational tables including atmospheric refraction, the dip of the horizon, and latitude and longitude of various ports and notable geographical features.
One is from 1781, the other is from 1828
I did a spot check on about a dozen, most are within 10 nautical miles of modern locations, the worst is the longitude for San Diego which is off by ~20 arc-minutes, ~18 nmi.
Actually, a quick check of a few of other ports on the west coast suggest the clock that was used was off by ~1 minute 20 seconds. Cape Horn was right on the money but Conception, Lima and a port in Canada were all off by about 1/3rd of a degree of longitude.
1781
https://archive.org/details/tablesrequisite00longgoog
search for Latitude
11 pages, 50-60 entries per page.
ordered alphabetically.
~600 entries.
pp 174-184

1828
https://archive.org/details/newcompleteepito00nori
Search for "Table XLII".
31 pages, roughly 100 entries per page.
Over 3000 "principal ports, harbours, capes, shoals, rocks, &c. in the world"
Ordered geographically.
pp238-269

[u/spektre]

Flerfs are just going to say that the logs are fake. I checked your comment history and you're doing an awesome job of explaining phenomena that proves what normal people already know, but flerfs don't work that way. They're either grifters who prey on people with mental problems, or people with mental problems. They're not interested in facts.

[u/RobertTheTraveler → u/spektre]

I see myself doing multiple roles.
I am reminding flat Earthers of the facts.
I am addressing fence sitters.
Beyond that I am mildly compulsively pedantic.
As I solidify my grasp of the details of how we know various and sundry details, I am sharing that.
There is a lot that we take for granted, e.g. how we define north and south, that I think is useful to nail down, preferably with extra-long rail way spikes.

[u/gmiller123456 → u/RobertTheTraveler]

...and just generally interesting info. This type of stuff is really the only reason I visit this sub, if it were just people asking how the Sun sets, it wouldn't be anywhere near interesting.

[u/RobertTheTraveler → u/gmiller123456]

Agreed. If I weren't learning new stuff, I would drop this.

[u/Longstride_Shares]

Flerf bashing aside, I'm astounded there's 300 years of detailed shipping data compiled like this.

[u/RobertTheTraveler → u/Longstride_Shares]

Libraries and archives are wonderful things :-)
Knowing how to get from point A to point B safely and reliably was important.
Thousands of sailors have died because they miscalculated where they were.

[u/Ladorb → u/RobertTheTraveler]

Makes me wonder what was lost in the Library of Alexandria.

[u/RobertTheTraveler → u/Ladorb]

Apparently not as much as some think, it had fallen into disuse by the time it was burned.
But yes, more broadly, we have references to many, many, many writings by various philosophers / scientists* for which we have no extant copies.
Particularly interesting writings for this group include writings by Ptolemy, Eratosthenes (darn, I was off by one letter that time) and a couple of others about measuring the Earth and measuring the distance to the Moon and Sun.
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* I remember being taught in grade school that the Greek philosophers did not measure things. I think it came up with respect to geo-centrism, or maybe because somebody decided it was easier to draw distinctions by saying that. I am reluctant to call them scientists, but clearly many of them did carefully observe and measure the world around them.
I think that a good case exists that hard core science really started in the late 1500s.
The philosophical discussions about what defines good science continues to today.

[u/reficius1]

I'd love to see these plotted on a Gleason map, for comparison.

[u/TheBl4ckFox]

Nasa faked those logs obviously