Approximate maximum distance to an over the horizon object versus the eye height of the observer
Enter height of object	H(1)		feet
Object to horizon distance	D(1)		miles
Enter eye height of observer	H(2)		feet
Observer to horizon distance	D(2)		miles
Oserver to object distance	D(3)		miles
Note that the above approximation applies for a ‘smooth’ earth surface such large lakes, oceans and level plains or deserts were surface irregularities are small compared to object or eye height and both are less than 50,000 feet