Radar Observer · Performance — Radar Horizon
Using radar horizon ≈ 1.22 × √(antenna height in feet), how far is the radar horizon for a scanner 64 feet above the water?
- A7.32 NM
- B9.76 NM✓ Correct
- C12.2 NM
- D4.88 NM
Explanation
Radar horizon ≈ 1.22 × √64 = 1.22 × 8 = 9.76 NM. Radar waves bend slightly more than light (the 1.22 factor vs 1.17 for the visual horizon), so the radar horizon is a little farther than the visible one. A target is first detected at roughly the sum of the scanner's and the target's radar horizons.
Authority: Bowditch (Pub. No. 9), Radar
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