Engineering Tools / Conversions


Useful Conversions and Rules of Thumb

1 foot (ft) = 0.3048 meters (m) 1 kilometer (km) = 0.54 nautical miles (nm) 1 stat. mile/hr = 1.61 km/hr
1 inch (in) = 0.0254 meters (m) 1 kilometer (km) - 0.54 knots (kt) 1 knot = 1.15 stat. mile/hr
1 yard (yd) = 0.9144 meters (m) 1 kilometer (km) = 0.62 statute miles (sm) 1 ft/sec = 0.59 knot = 1.1 km/hr
    1 stat.mile = 0.878 naut.mile
Speed of light = 2.9979246 x 108 m/s (approx 3x108 m/s)
Speed of sound = 343.2 m/s (dry air at 20°C (68°F))
Speed of sound = MACH 1
Speed of sound (Sea Level) = 1235 km/hr
Speed of sound (36,000 Feet) = 1062 km/hr (TAS)

Radar Equations

The power Pr returning to the receiving antenna is given by the equation:

where
♦ Pt = transmitter power ♦ σ = radar cross section, or scattering coefficient, of the target
♦ Gt = gain of the transmitting antenna ♦ F = pattern propagation factor (1 for a vacuum)
♦ Ar = effective aperture (area) of the receiving antenna ♦ R = distance from the transmitter / receiver to the target