# radar line-of-sight (LOS) equation

**radar line-of-sight (LOS) equation:** An equation that expresses the radar horizon range (RHR), given by where *RHR*_{s} is the radar horizon range in statute miles, *h* is the antenna height in feet, and *a* is the object critical altitude, *i.e.,* the target altitude in feet, below which the radar cannot illuminate the object. *Note:* The RHR is also given by

where *RHR*_{k} is the radar horizon range in kilometers when *h* and *a* are in meters. The effective Earth radius, namely 4/3 times the actual Earth radius, is used in deriving these formulas. The effective Earth radius for LOS varies with carrier frequency. Second-order differentials are neglected. They contribute less than 0.1%. [From Weik '89]

This HTML version of FS-1037C was last generated on Fri Aug 23 00:22:38 MDT 1996