ASTB

• 1. Pressure
• a. pressure is the weight of the atmosphere
• b. atmosphere pressure is heavier closer to the earth's surface

• 2. Temperature
• a. as temperature increases density decreases

• 3. Humidity
• a. as humidity increases, density decreases
• b. water weighs less than air

Pressure Altitude corrected for non standard temperature

For every inch of Hg gained you lose 1000 feet of altitude

For ever inch of Hg lost you gain 1000 feet of altitude

Height above ground measured in AGL

M.S.L measurement

Altitude indicated when you set the altimeter to 29.92 Hg.

Altitude read of the altimeter when set to local m.s.l pressure from ATIS