From: kym@kymhorsell.com   
      
   Skybuck Flying  wrote:   
   > On Thursday, December 15, 2022 at 12:07:54 AM UTC+1, R Kym Horsell wrote:   
   >> Skybuck Flying  wrote:   
   >> > Hello,   
   >> ...   
   >> OK. I have saved that away to look throuh slowly.   
   >> A first comment on something I saw on way through -- calculating   
   >> the distance between 2 points on a sphere or almost-sphere is   
   >> by a simple formula "great circle distance".   
   > It is probably not accurate enough and has issues near the poles.   
      
   Oh, sure. The earth is not a sphere. But why do you need to determine   
   the actual "over the earth" distance to better than 1 part in 1000?   
      
   I had guessed you might want to be able to tell someone at one location   
   where in their sky an object might be that is now being seen at   
   some other location. But that can be done well within say 1 degree --   
   a finger width -- using the low-grade GPS co-ords the phone is sending   
   out all the time.  You dont even need the great circle distance for that --   
   just the x,y and z of the 2 points.   
      
   > There seems to be a better more accurate method, but the math is even harder:   
   > https://link.springer.com/article/10.1007/s00190-012-0578-z   
   > If you must know what kind of problems the great circle method has then the   
   same author wrote about it here:   
   > https://arxiv.org/abs/1102.1215   
   > Bye for now,   
   >  Skybuck.   
      
   --- SoupGate-Win32 v1.05   
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