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The altitude indicated on the altimeter is correct only if the sea level barometric pressure is standard (29.92 "Hg), the sea level free air temperature is standard (+15 °C or 59 °F), and the pressure and temperature decreases at a standard rate with an increase in altitude. Since atmospheric pressure continually changes, a means is provided to adjust the altimeter to compensate for nonstandard conditions. This is accomplished through a system by which the altimeter setting (local station barometric pressure reduced to sea level) is set to a barometric scale located on the face of the altimeter. Only after the altimeter is set properly will it indicate the correct altitude. 

## Effect of Nonstandard Pressure and Temperature 

If no means were provided for adjusting altimeters to nonstandard pressure, flight could be hazardous. For example, if a flight is made from a high-pressure area to a low-pressure area without adjusting the altimeter, the actual altitude of the glider is lower than indicated altitude. When flying from a low-pressure area to a high-pressure area, the actual altitude 

