# What is the difference between TAS and GS? [duplicate]

I'm looking for an explanation of true airspeed and ground speed.

• The difference between them is the wind speed. TAS + Wind = GS
– Jan
Aug 11, 2019 at 14:37
• If you know what the abbreviations mean then this question answers itself! Aug 11, 2019 at 15:58

TAS = True Airspeed = speed that you get on radar gun as airplane flies by, when radar gun is held by someone in gondola of balloon in same airmass (wind motion) as airplane.

GS =Groundspeed = speed that you get on radar gun as airplane flies by, when radar gun is held by someone on ground.

As an example: TAS of 200 knots and a headwind of 20 knots gives a GS of 200-20=180 knots. That is: the plane travels at 180 knots over ground but the air is flowing past the plane at 200 knots.

• Weird phone screw-up there! Aug 11, 2019 at 14:37
• Feel free to add via editing (or post own); I'm not emotionally attached to ownership of this answer :) Aug 11, 2019 at 15:05
• Edited to fix units and avoid issue with what you "feel" with hand being a better description of IAS than TAS. Aug 11, 2019 at 22:05
• Pythagoras would like to have a word with you about your "GS" definition. Aug 11, 2019 at 22:48
• @JacobKrall - ok I get it. The radar gun should not be triggered until a/c is flying nearly directly away... Aug 12, 2019 at 12:06

True air speed is the speed in relation to the mass of air you are moving in, and ground speed is the speed in relation to the ground.