How does an Hour Angle Watch works ?

[@isaiasflorenca7461]

Excellent video! I have the beautiful Lindbergh Hour Angle watch and could not work out how the navigation system works.

[@fpab6534]

This was an amazing video. Well done, thanks for sharing.

[@rumblejungle5590]

It's just a conversion scale between units of time and units of arc. In practice navigators (back in cel nav days) did not determine their longitude by subtracting local from GMT since they only knew their local time once they had determined their longitude. There is a very old cel nav method to determine local time directly which was used in the days when mariners didn't have accurate clocks, but it had long been too imprecise and unpractical by the time air navigation had arisen.

[@dukecraig2402]

There's an excellent made for TV mini series that originally aired on A&E called Longitude, it stars Micheal Gambon as John Harrison the inventor of the marine chronometer, the timepiece for determining a ships longitudinal position at sea, Jeremy Irons also stars in it. Unlike most movies that their subject is historical this one gets it right and doesn't distort historical facts for the sake of drama, it's really a good watch (no pun intended), I believe it can be seen on Amazon Prime these days.

[@amintaslneto]

Great video. Thanks for sharing

[@ReformMsia]

Love this video well made

[@freshramses]

Very interesting!

[@himanshubhatnagar1495]

How do they know their latitude ? Or is it assumed that they know their latitude and with this watch they can also know their longitude and hence their position?

[@elgoog-the-third]

Finding out the latitude is what the sextant is for.

[@BGCflyer]

With a sextant you can get the angle of the sun to the horizon at your local noon time or when the sun is at its highest point in the day, note the current time, then make a mathematical adjustment for altitude and another adjustment with the nautical almanac based on the day of the year. The same can be done at night with the angle of the North Star and the horizon.

[@SA-gf3th]

You didn't account the fact that there's something called equation of time adjustments.

[@rumblejungle5590]

No, pilots could not work their latitude out any more readily than they could work out their longitude. You might be confusing pilots with maritime navigators prior to precise timekeeping.

[@videosrus99]

01:02 "Pilots could work out their latitude whilst in flight". How?

[@phmwu7368]

@@videosrus99 Need to see the Sun, measure Sun angle to horizon (quadrant or sextant), check nautical almanac Sun declination for that date, corrected Sun angle = Lat

[@rumblejungle5590]

@@phmwu7368 You can't do that without knowing local time and your watch will just measure time with no refernce to any location. Even so, simply subtracting from the angle from the sun's declination only works if the sun is precisely north or south and close to the equator during the day you may not even know whether it's north or south, never mind precisely. You assume that you're on a point on a map from a known last position. Usually you have some idea within 100-200 miles that you're in. Then you measure the angle of the sun. Look up azimuth for the current time and for the position you assume yourself to be in, it doesn't matter which location though GMT can be read off straight from the almanac. The azimuth in this case is the line from your position to the point exactly below the sun on earth ( in other cases it's the line to your actual position). Then you can plot the line connecting all points on the map on which the sun is at the measured angle since at that scale where you can easily make out 20 miles and unless you're measuring the sun's angle at noon around the equator it can comfortably be plotted on your (Mercator) map as a straight line, by drawing a straight line perpendicular to the azimuth at a distance from straight underneath the sun at 0 degrees of arc to, theoretically, 90 degrees of arc. 1 arc minute is roughly a mile though it will depend on the point of projection of your map. If you have no idea where you are, which is usually hypothetical you can work out your position by solving the geometric equations, but that again is usually not necessary.

[@cap5364]

Is that Jude Law speaking?