Altimeter
The altimeter measures the height of the glider above sea level. The SCOH glider port is 300 feet above sea level so the altimeter should indicate 300 feet if it is set correctly and the glider is on the ground at SCOH.
PRINCIPLE OF OPERATION
The pressure altimeter is simply an aneroid barometer that measures the pressure of the atmosphere at the level where the altimeter is located, and presents an altitude indication in feet. The altimeter uses static pressure as its source of operation. Air is denser at the surface of the Earth than aloft, therefore as altitude increases, atmospheric pressure decreases. This difference in pressure at various levels causes the altimeter to indicate changes in altitude.