true altitude

[′trü ′al·tə‚tüd]

(meteorology)

true altitude

i. The actual height above sea level. The calibrated altitude corrected for air temperature. See altitude.
ii. The actual altitude of a celestial body above the celestial horizon. The observed altitude must be corrected for several variables before it becomes the true altitude.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

True Altitude

(also, absolute altitude), in geodesy, the distance along a vertical from a given point on the surface of the earth to sea level. It is determined by leveling. In the USSR, true altitude is calculated from zero on the depth gauge in Kronstadt.

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References in periodicals archive

Even with the correct altimeter setting your barometric altitude can differ from your true altitude by as much as 10 percent.

The dangers of GPS altitude

Airport, terrain and obstacle elevations on aeronautical charts are true altitudes.

Beyond the MEA: getting as low as possible while remaining IFR can mean a non-stop, light or getting in on a visual. Asking ATC often is the key

Absolute altitude is the height above terrain computed by subtracting terrain elevation from true altitude.

Your altimeter lies: but its falsehoods are known and predictable, and regular inspections and maintenance can uncover them. Just pay close attention in cold weather

In these cases, unless the altimeter setting is adjusted, the height of the pressure level corresponding to the current altimeter setting, and therefore, true altitude, will decrease--we'll be lower than we realize.

Cold altitudes

Remember that heavy smokers can increase their true altitude by 5000 to 8000 feet when considering oxygen use and TUC.

O2 realities: the FARs say one thing about when to use oxygen but the reality is quite different. You probably need it sooner and lower

Your indicated altitude is corrected for non-standard pressure, but would also need to be adjusted for non-standard temperature as well as pressure differences between your position and the reporting weather station in order to obtain your true altitude. Oh, and the altimeter is electric, so it's not reliable anyway.

Panel by IPAD

Altitude is true altitude (your actual height above sea level) as determined by your GPS position and is quite accurate even when compared to a properly set altimeter.

Handheld six-pack? Garmin's late-model GPS navigators feature a built-in virtual panel to use when the real one soils the bed. What it can do, how it works and how to use it

In practice, nonstandard temperatures affect all aircraft equally, so all aircraft at an indicated altitude will still be on the same horizontal plane, even though the true altitude of that plane shifts with temperature.

Watch your step(down): having a glideslope to follow always feels better than being without one. But if you intercept the glideslope early, you must adhere to any stepdown fixes prior to the FAF ... right?

The fact that the area he is flying in is not designated as mountainous does not change the fact that it is mountainous, and altimeter errors due to venturi effects, etc., can make the indicated altitude higher than true altitude. Some local knowledge and experience may allow one to make proper judgments about these effects in the specific location, but in general, one should be cautious and conservative.

User fees and ADIZ training

The FB Winds are provided to pilots at true altitudes every 3000 feet through 12,000 feet and pressure altitudes every 6000 feet at or above 18,000 feet.

Using winds aloft: winds aloft forecasts are one of your best tools for flight planning and fuel saving, but you need to know the whole story