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Ark Shvetsky wrote:
> Thank you, Frank!
>
>
> Just wants to make it clear for myself :>: to calculate a distance to the 
visible horizon I need to use statute miles, not nautical.  Is this a correct 
statement?
>   
No -- the Bowditch formulas are for distance to horizon in nautical 
miles.  

As an aside, as Frank pointed out the distance-to-the-horizon figure can 
vary depending on the amount of refraction, which in turn depends on 
atmospheric conditions.  Because it's not a three-digit-accuracy 
calculation, I prefer to use 8/7 as the multiplier rather than 1.15 (or 
1.17 or other numbers given in Bowditch or other publications over the 
years).   It's a lot easier to remember and a lot easier to use in 
mental calculations (and even arguably fewer keystrokes on a calculator).
> Also, just curious: radio waves and light wave are electromagnetic waves 
which are differ in frequency.  Therefore, it means the refraction-wise high 
frequency signal is refracted more.  Is it logarithmic or just a linear 
correlation for refraction rate between low and high frequency waves?
The lower the frequency, the greater the refraction.  But there are many 
factors that contribute to refraction -- for light, it's primarily the 
density of the atmosphere.  But for lower frequency electromagnetic 
radiation, its primarily the conductivity of the surface of the earth.  
So to the best of my knowledge, there's no simple linear-vs-logarithmic 
answer.

Lu Abel

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