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Mechanical clock accuracy used to be pretty important for navigation to determine longitude. A large prize was offered by the British government to whoever coul

Mechanical clock accuracy used to be pretty important for navigation to determine longitude. A large prize was offered by the British government to whoever could invent a way to accurately determine longitude. It's an interesting look at the high-tech world of yesteryear. https://watchesbysjx.com/2019/09/john-harrison-marine-chronometer-h4-diamond-pallets.html https://watchesbysjx.com/2019/09/john-harrison-marine-chrono... https://en.m.wikipedia.org/wiki/Longitude_rewards https://en.m.wikipedia.org/wiki/Longitude_rewards

HPsquared 3y ago
(Too late to edit) And, of course, clock accuracy is even more critical now in the age of GPS.
- 15457345234 3y ago
  Technically yes but the user of that system doesn't have to have an accurate clock, the GPS system itself provides the time signal. I think the first stage of GPS positioning is clock signal acquisition and training the local oscillator. Once synced you can proceed with almanac download or whatever comes next. (The accurate (atomic) clocks are on the satellites and base stations.)
  - nequo 3y ago
    Seiko also builds watches that use GPS signals to set the time zone and the time.[1] Seems like a cool idea if you cross time zones often and have an extra $2,000 on your hands. [1] https://www.seikowatches.com/us-en/products/astron/features_gps https://www.seikowatches.com/us-en/products/astron/features_...
    - throw0101a 3y ago
      As does Citizen: * https://www.citizenwatch.com/ca/en/technology-satellite-timekeeping.html https://www.citizenwatch.com/ca/en/technology-satellite-time...
    - WalterBright 3y ago
      My phone does that, too !!
      - 15457345234 3y ago
        I think most phones with a GPS receiver don't use it for time, they use the native network time signal instead. This is annoying as the (formerly) GSM time signal in many cases used to be _way_ off, like, 5-10 seconds off. This situation has improved somewhat in the last 10 years or so.
    - killingtime74 3y ago
      Um, most gps sports watches do. There are even ones that are multi-band gps (L1/L5)
  - AlotOfReading 3y ago
    GPS receivers are required to have excellent stability (<<1ppm), but not accuracy. The problem of marine chronometry was also about stability and not accuracy. After all, if you have a stable but inaccurate clock and can't tune it for some reason, it's straightforward to compensate for the offset when measuring to calculate your position.
throw0101a 3y ago
> Mechanical clock accuracy used to be pretty important for navigation to determine longitude. Specifically: > One degree of latitude equals approximately 364,000 feet (69 miles), one minute equals 6,068 feet (1.15 miles), and one-second equals 101 feet. One-degree of longitude equals 288,200 feet (54.6 miles), one minute equals 4,800 feet (0.91 mile), and one second equals 80 feet. * https://www.usgs.gov/faqs/how-much-distance-does-a-degree-minute-and-second-cover-your-maps https://www.usgs.gov/faqs/how-much-distance-does-a-degree-mi... > One minute of latitude covers about 1.8 kilometers (1.1 miles) and one second of latitude covers about 32 meters (105 feet). * https://education.nationalgeographic.org/resource/latitude/ https://education.nationalgeographic.org/resource/latitude/ When using a sextant: > Sextants measure the angle between the sea horizon and a celestial body. These angles are measured in degrees and minutes of arc (1/60th of a degee). Measuring this angle to an accuracy of 1 minute of arc (1') will result in a positional accuracy of 1 nautical mile. Accurate sextants can measure this angle to an accuracy of 0.2'. This means that theoretically one can determine their position to 1/5 of a mile [~320m]. Additionally, a good clock is required to accurately compute the GP of the celestial body. An error of 1 second in the clock will create a positional error of up to 1/4 of a mile [~400m]. * http://www.cse.yorku.ca/~amana/personal/navigation/ http://www.cse.yorku.ca/~amana/personal/navigation/ Airplanes also used to use sextants for trans-oceanic flights (when beyond radio beacon range). Part 63 of FAA regulations has a section on Flight Navigators: * https://www.ecfr.gov/current/title-14/chapter-I/subchapter-D/part-63/subpart-C https://www.ecfr.gov/current/title-14/chapter-I/subchapter-D... Doing a search for FAA-H-8083-18 will lead you to The FAA Flight Navigator Handbook.
- WalterBright 3y ago
  My dad was navigator on a B-17 in WW2. The B-17 crews had to fly their own birds from Newfoundland to England. Many crews and their airplanes were lost without a trace on this trip. (There was no hope of rescue if you went down in the North Atlantic. You just prayed nothing went wrong with the engines or the navigation.) My dad was proud he crossed the coast of Ireland within a mile of where he was aiming for. His tool was a sextant and math. He was made lead navigator for his bomb group. He wanted to be a pilot, but because he was a math nerd, the Air Corps told him he was gonna be a navigator.
Terr_ 3y ago
In an alternate universe, people might've discovered simple radio first, and skipped all the fancy clock developments! 1. Set up a big transmitter in some major city that fires off a big noisy pulse at every day at solar-noon. 2. Equip your long-distance ships with mediocre clock and a radio-receiver that is just good enough to detect the pulse if a crewmember is waiting and listening for it. 3. Using the low-accuracy clock, measure the difference between (A) solar noon where the ship is and (B) when the radio-pulse is received. Every 4 minutes is 1 degree of longitude. P.S.: The pulse-listener will have to shift their listening-window as the ship travels, but it shouldn't be too tough since they already have a so-so clock and know their latitude. Sailing 200km/day along the equator means the pulse-listener would have to adjust their listening-window by ~8 minutes/day to keep "centered" on the pulse moment.
deleted 3y ago
[deleted]
JohnBooty 3y ago
The more I learn about old-timey maritime navigation, the more I realize that (like a lot of skilled trades) it must have been nearly indistinguishable from literal magic to laypeople. I wonder if that fact inspired the mysterious and bizarre Guild Navigators in Dune.

HPsquared 3y ago

(Too late to edit) And, of course, clock accuracy is even more critical now in the age of GPS.

15457345234 3y ago
Technically yes but the user of that system doesn't have to have an accurate clock, the GPS system itself provides the time signal. I think the first stage of GPS positioning is clock signal acquisition and training the local oscillator. Once synced you can proceed with almanac download or whatever comes next. (The accurate (atomic) clocks are on the satellites and base stations.)
- nequo 3y ago
  Seiko also builds watches that use GPS signals to set the time zone and the time.[1] Seems like a cool idea if you cross time zones often and have an extra $2,000 on your hands. [1] https://www.seikowatches.com/us-en/products/astron/features_gps https://www.seikowatches.com/us-en/products/astron/features_...
  - throw0101a 3y ago
    As does Citizen: * https://www.citizenwatch.com/ca/en/technology-satellite-timekeeping.html https://www.citizenwatch.com/ca/en/technology-satellite-time...
  - WalterBright 3y ago
    My phone does that, too !!
    - 15457345234 3y ago
      I think most phones with a GPS receiver don't use it for time, they use the native network time signal instead. This is annoying as the (formerly) GSM time signal in many cases used to be _way_ off, like, 5-10 seconds off. This situation has improved somewhat in the last 10 years or so.
  - killingtime74 3y ago
    Um, most gps sports watches do. There are even ones that are multi-band gps (L1/L5)
- AlotOfReading 3y ago
  GPS receivers are required to have excellent stability (<<1ppm), but not accuracy. The problem of marine chronometry was also about stability and not accuracy. After all, if you have a stable but inaccurate clock and can't tune it for some reason, it's straightforward to compensate for the offset when measuring to calculate your position.

throw0101a 3y ago

> Mechanical clock accuracy used to be pretty important for navigation to determine longitude. Specifically: > One degree of latitude equals approximately 364,000 feet (69 miles), one minute equals 6,068 feet (1.15 miles), and one-second equals 101 feet. One-degree of longitude equals 288,200 feet (54.6 miles), one minute equals 4,800 feet (0.91 mile), and one second equals 80 feet. * https://www.usgs.gov/faqs/how-much-distance-does-a-degree-minute-and-second-cover-your-maps https://www.usgs.gov/faqs/how-much-distance-does-a-degree-mi... > One minute of latitude covers about 1.8 kilometers (1.1 miles) and one second of latitude covers about 32 meters (105 feet). * https://education.nationalgeographic.org/resource/latitude/ https://education.nationalgeographic.org/resource/latitude/ When using a sextant: > Sextants measure the angle between the sea horizon and a celestial body. These angles are measured in degrees and minutes of arc (1/60th of a degee). Measuring this angle to an accuracy of 1 minute of arc (1') will result in a positional accuracy of 1 nautical mile. Accurate sextants can measure this angle to an accuracy of 0.2'. This means that theoretically one can determine their position to 1/5 of a mile [~320m]. Additionally, a good clock is required to accurately compute the GP of the celestial body. An error of 1 second in the clock will create a positional error of up to 1/4 of a mile [~400m]. * http://www.cse.yorku.ca/~amana/personal/navigation/ http://www.cse.yorku.ca/~amana/personal/navigation/ Airplanes also used to use sextants for trans-oceanic flights (when beyond radio beacon range). Part 63 of FAA regulations has a section on Flight Navigators: * https://www.ecfr.gov/current/title-14/chapter-I/subchapter-D/part-63/subpart-C https://www.ecfr.gov/current/title-14/chapter-I/subchapter-D... Doing a search for FAA-H-8083-18 will lead you to The FAA Flight Navigator Handbook.

WalterBright 3y ago
My dad was navigator on a B-17 in WW2. The B-17 crews had to fly their own birds from Newfoundland to England. Many crews and their airplanes were lost without a trace on this trip. (There was no hope of rescue if you went down in the North Atlantic. You just prayed nothing went wrong with the engines or the navigation.) My dad was proud he crossed the coast of Ireland within a mile of where he was aiming for. His tool was a sextant and math. He was made lead navigator for his bomb group. He wanted to be a pilot, but because he was a math nerd, the Air Corps told him he was gonna be a navigator.

Terr_ 3y ago

In an alternate universe, people might've discovered simple radio first, and skipped all the fancy clock developments! 1. Set up a big transmitter in some major city that fires off a big noisy pulse at every day at solar-noon. 2. Equip your long-distance ships with mediocre clock and a radio-receiver that is just good enough to detect the pulse if a crewmember is waiting and listening for it. 3. Using the low-accuracy clock, measure the difference between (A) solar noon where the ship is and (B) when the radio-pulse is received. Every 4 minutes is 1 degree of longitude. P.S.: The pulse-listener will have to shift their listening-window as the ship travels, but it shouldn't be too tough since they already have a so-so clock and know their latitude. Sailing 200km/day along the equator means the pulse-listener would have to adjust their listening-window by ~8 minutes/day to keep "centered" on the pulse moment.

deleted 3y ago

[deleted]

JohnBooty 3y ago

The more I learn about old-timey maritime navigation, the more I realize that (like a lot of skilled trades) it must have been nearly indistinguishable from literal magic to laypeople. I wonder if that fact inspired the mysterious and bizarre Guild Navigators in Dune.