Altitude

Altitude is the vertical distance of a level, point, or object measured above mean sea level (MSL). It is one of the fundamental positional parameters in aviation and differs from height (measured above a local surface or datum) and elevation (the altitude of a fixed point on the earth’s surface).

Types of Altitude

• Indicated altitude: Read directly from the altimeter with current QNH set; the standard reference in Canadian airspace below FL180
• True altitude: Actual height above MSL; differs from indicated in non-standard temperature conditions
• Absolute altitude: Height above the terrain directly below — AGL
• Pressure altitude: Indicated altitude with 29.92 inHg set; used for performance calculations and above FL180
• Density altitude: Pressure altitude corrected for non-standard temperature; the altitude the aircraft “feels” for performance purposes

VFR Cruising Altitudes

In Canada, VFR cruising altitudes at and above 3,000 ft AGL follow the magnetic track rule: 0°–179° fly at odd thousands + 500 ft (e.g., 3,500, 5,500); 180°–359° fly at even thousands + 500 ft (e.g., 4,500, 6,500). This provides 1,000 ft vertical separation between opposing traffic.

On the TC Written Exam

Altitude type definitions are heavily tested. The VFR cruising altitude rule is a guaranteed exam question. Most critically: density altitude is the performance-relevant altitude and can be thousands of feet above field elevation on a hot, high-elevation day.

Related Terms

See also: Absolute Altitude, True Altitude, Pressure Altitude, Density Altitude, Altimeter.