Kestrel
®
4500 Pocket Weather
®
Tracker
Density Altitude
The altitude at which you would be, given the current air density. Often used by pilots in order to
determine how an aircraft will perform. Also of interest to individuals who tune high performance
internal combustion engines, such as racecar engines.
Dewpoint
The temperature to which air must be cooled in order for condensation to occur. The difference between
dewpoint and temperature is referred to as the “temperature/dew point spread”. A low dewpoint spread
indicates high relative humidity, while a large dewpoint spread indicates dry conditions.
Heat Index
A practical measure of how hot the current combination of relative humidity and temperature feels to a
human body. Higher relative humidity makes it seem hotter because the body’s ability to cool itself by
evaporating perspiration is reduced.
Magnetic North
The point on the Earth’s surface where the Earth’s magnetic field points directly downwards. This pole is
constantly wandering.
Reference Pressure
The local barometric pressure. Input to the altitude screen to provide correct altitude readings. Also
known as the altimeter setting.
Relative Humidity
The amount of water vapor actually in the air divided by the maximum amount of water vapor the air
could hold at that temperature, expressed as a percentage.
