[HN Gopher] Ships must practice celestial navigation
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       Ships must practice celestial navigation
        
       Author : HR01
       Score  : 13 points
       Date   : 2025-01-10 16:39 UTC (6 hours ago)
        
 (HTM) web link (www.usni.org)
 (TXT) w3m dump (www.usni.org)
        
       | jas39 wrote:
       | A smartphone has all the sensors: tilt, clock, camera. Even
       | compass, though hardly needed. This should be enough to build an
       | app to determine position at sea.
        
         | bhhaskin wrote:
         | Those likely aren't anywhere near accurate enough. And accuracy
         | matters when being off by a few degrees can mean hundreds of
         | miles.
        
           | UniverseHacker wrote:
           | You're right, but they can be used together with a sextant to
           | instantly preform calculations that can be time consuming and
           | difficult at sea.
           | 
           | I use an app to double check my hand calculations.
        
             | bhhaskin wrote:
             | At that point though you are using a sextant and a fancy
             | calculator =P
        
         | saulpw wrote:
         | But what happens when the smartphone is bricked by an EMP, or
         | hacked by a nation-state virus? Haven't you ever seen
         | Battlestar Galactica?
        
       | _xerces_ wrote:
       | Curious how navigation at night was not possible without
       | expensive equipment, sounds like they were relying only on starts
       | in the morning and evening? Are the measuring something like
       | angle of those morning/evening stars or their set/rise times with
       | respect to the sun?
        
         | UniverseHacker wrote:
         | It is not true- the authors sound very inexperienced with
         | celestial navigation. There are many ways including the lunar
         | distance method to get a position at night with regular
         | equipment. The math is more complex than a simple noon solar
         | sighting, but it can be done with just a regular cheap plastic
         | sextant and a watch.
         | 
         | It's also no big deal to go 12 hours with no position. If you
         | know your speed and heading you can accurately estimate your
         | position much longer than that.
         | 
         | Overall, they also made it sound almost impossibly difficult
         | for a large team of professionals, when solo and otherwise
         | short handed recreational sailors have been reliably sailing
         | around the world with celestial navigation for more than a
         | century- through all possible conditions.
        
         | quercusa wrote:
         | And just how expensive _is_ a bubble sextant?
        
       | throw0101a wrote:
       | Training for this was first discontinued, but brought back in
       | 2016:
       | 
       | * https://www.npr.org/2016/02/22/467210492/u-s-navy-brings-bac...
       | 
       | Now if only the US (and others) would get their act together and
       | build out a backup system to GNSS. China, for example, has built
       | out an eLoran system:
       | 
       | * https://rntfnd.org/2024/10/03/china-completes-national-elora...
        
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       (page generated 2025-01-10 23:02 UTC)