Calculate the distance to the radar horizon and maximum detection range considering atmospheric refraction.
Height Parameters
Distance Estimates
Enter heights to calculate
About this calculator
Quick Reference
h1Antenna height
h2Target height
4/3 RadiusStandard refraction model
1 nmi1.852 km
Overview
The radar horizon is further than the optical horizon because radio waves are refracted by the atmosphere. This is usually modeled by using an 'effective Earth radius' of 4/3 the actual radius.
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Pro Tips
h1 is the height of the radar antenna above sea level.
h2 is the height of the target being detected.
The formula used is d ≈ 4.12 * (√h1 + √h2) for metric units.
Standard refraction adds about 6% to the optical horizon distance.
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Fun Facts
"Over-the-horizon (OTH) radars can detect targets thousands of miles away by bouncing signals off the ionosphere."
"The 4/3 Earth radius model is a standard approximation for radio propagation."
"Super-refraction or 'ducting' can sometimes allow radar to see much further than normal."
