Method and system for calculating altitude above runway for an aircraft

An article of manufacture comprising computer program code embodied in computer-readable medium comprising instructions that when executed are used to compute a synthetic altitude above a runway, the method comprising:

• receiving horizontal distance information of the distance from an aircraft to a runway threshold associated with a runway, the surface of the runway defining a runway plane;
• determining a projected ground distance from the aircraft to the runway threshold;
• determining a distance from the runway threshold to a glide path intercept point based on a projected aircraft glide path angle and a threshold crossing height;
• determining a current height of the aircraft above the runway plane based on the projected ground distance and the distance from the runway threshold to a glide path intercept point;
• and
• determining an aircraft synthetic altitude above the runway plane based on the current height of the aircraft and a predetermined vertical error or angular deviation component.