Calculator below computes the prospect distance from height at observer and line of sight distance between two observers. Some theory is placed below the calculator.
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As shown on piture, observer's view is limited by horizon - imaginary line where sky touches the earth. According to picture we can calculate distance to the horizon from Pythagoras theorem.
where R - is Earth radius, usually taken as 6378 kilometers.
Atmospheric refraction increases the prospect distance by over 6 percent.
The result formula is
Simplified formula, which can be deduced from above, is often used
, for nautical miles or
, for kilometers
Line of sight
As shown on picture, line of sight distance is simply addition of two prospect distances.