About Radar Horizon Planning
A radar horizon calculator estimates how far a radar can see before Earth curvature blocks the beam. The value depends mainly on radar antenna height, target height, Earth radius, and atmospheric refraction. A higher radar antenna increases the tangent distance. A higher target also extends the possible detection range. The combined range is the sum of both horizon distances.
Why Refraction Matters
Radio waves often bend slightly through the lower atmosphere. This bending makes Earth appear larger to the signal path. Engineers commonly model that effect with a K factor. A K value of one represents optical geometry. A K value of 1.333 is often used for standard radio planning. Larger values produce longer calculated horizons. Smaller values produce conservative ranges.
Practical Use Cases
This tool helps with marine radar checks, coastal surveillance planning, tower placement, field link reviews, and training examples. It is also useful when comparing sensor heights before equipment is installed. The planned range field lets you test a desired path. The result shows whether the entered range fits inside the calculated horizon. It also shows a reserve after your selected safety allowance.
Understanding the Result
The calculator reports the radar horizon, target horizon, total line of sight range, and converted values in kilometers, statute miles, and nautical miles. Exact mode uses the tangent distance from an effective Earth radius. Approximate mode uses the common short distance square root equation. For ordinary tower heights, both methods are usually close. Exact mode is better when heights are large.
Planning Notes
Radar horizon is not the same as guaranteed detection. Power, antenna gain, wavelength, clutter, terrain, rain, ducting, target size, and receiver sensitivity also matter. Use this page as a geometry planner. Then confirm final performance with site surveys, link budgets, local terrain data, and equipment specifications. Keep a margin when safety or mission reliability is important.
Good Input Habits
Enter heights above the local surface, not above sea level, unless the radar path is referenced to a common datum. Use matching units. Choose the standard K factor for routine radio estimates. Use a conservative K factor when weather, terrain, or reliability is uncertain. Save the exported file with the site record for review.