Sample Form

Compute Range
Between 2 Targets
when Echo's Equal

The form below computes the range (and range difference) of two targets given both targets' Radar Cross Section (RCS) and one target's range. If INPUT range dimensions in feet, results are in feet; if INPUT range in meters, results are in meters, etc. Target range entered must be a whole number (no decimal point).

Sample Form Results

Range between Targets

Target Echoes Equal Power

Target 1 Target 2

Radar Cross Section (RCS) 30 m² 120 m²
Range to Radar 500 707
Range Between Targets 207

	Target 1	Target 2
Radar Cross Section (RCS)	30 m²	120 m²
Range to Radar	500	707
Range Between Targets	207

If INPUT range dimensions in feet, results are in feet;
if INPUT in meters, results are in meters, etc.

RCS₂ / RCS₁ = 4:1
(RCS₂ / RCS₁)^1/4 = 1.41
V₂ = 1.41 V₁

In the above example Target 1 (a small car with an RCS of 30 m²) 500 feet from the radar has the same signal echo power as Target 2 (a large car with an RCS of 120 m²) 707 feet from the radar (207 feet, 69 yards, behind Target 1). If both targets are traveling toward the radar, and Target 2 is traveling 1.41 times faster than Target 1, from this point on Target 2 and Target 1 have equal echo signals. If Target 1 speed is 50 mph, Target 2's speed must be 70.5 mph (1.41 x 50 = 70.5). If Target 2 is closer (than 707 feet from the radar) it's speed can be slower (than 1.41 times Target 1's speed) to maintain equal echo signals.

Police Traffic Radar Handbook
Chapter 2.2