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This question already has an answer here:

What is difference between ground speed and airspeed? Is ground speed used only for takeoff or is it used for flight too?

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marked as duplicate by fooot, Simon, voretaq7 Mar 4 '16 at 22:16

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  • $\begingroup$ Snarky answer: it's literally the magnitude of the component of the wind speed in the direction of travel. $\endgroup$ – Todd Wilcox Mar 4 '16 at 22:10
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    $\begingroup$ Not a duplicate... the referenced question is asking about a video game, and got an answer with more formulas than a college level Aero course. This question is asking for a straightforward answer to the concepts of airspeed and groundspeed, and aviation.se doesn't have that -- at least not in the referenced "duplicate" question. Voting to reopen. $\endgroup$ – Ralph J Mar 4 '16 at 22:25
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    $\begingroup$ You are headed east at an indicated 100mph, the air mass you are in is headed west at 10mph, your indicated air speed will be 100mph, the ground speed will be 90mph since you have a 10mph head wind. If the air mass were heading east (tail wind) at 10mph, your indicated airspeed would still be 100mph, but your ground speed would increase to 110mph. Make sense? $\endgroup$ – Ron Beyer Mar 4 '16 at 22:52
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    $\begingroup$ GPS speed is the same as Ground speed. The "Flight Simulator" video game question and answers are also applicable to real life so the question has been answered correctly. I vote to remain closed. $\endgroup$ – Mike Sowsun Mar 4 '16 at 23:16
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The ground speed is the speed the aircraft is making over ground below.

The indicated airspeed (IAS) is the speed shown on the airspeed indicator. This will be different than the ground speed for various reasons, such as wind and the attitude of the aircraft. For example, if the aircraft is diving then the IAS will be greater than the ground speed. In fact, if the aircraft were diving straight down, then the ground speed could be 0 while the IAS was hundreds of knots per hour.

The indicated airspeed is the usual measure used in flight.

The ground speed can be calculated to estimate the time of arrival of the aircraft at some destination.

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  • $\begingroup$ In my opinion this answer is poorly written. The answer should include information how Indicated airspeed relates to True airspeed and how True airspeed relates to Ground speed. The implication that difference between ground speed and indicated airspeed can be partially due to the aircraft diving is misleading and totally unnecessary. $\endgroup$ – Mike Sowsun Mar 4 '16 at 23:26
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    $\begingroup$ The question as posed I did not regard as requiring a detailed technical answer and such an answer I think would be more confusing than helpful for him. Getting into calibrated air speed, true airspeed, equivalent airspeed and so on is just overkill here and there are already other answers that cover such things. As for the example, I think it is useful to give a very simple and easy to understand example why IAS can differ from ground speed. $\endgroup$ – Tyler Durden Mar 5 '16 at 0:22
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    $\begingroup$ If you want to keep it really simple you could say that ground speed is the speed of the aircraft in relation to the ground, and that airspeed is the speed of the aircraft in relation to the air around it. The mass of air that the aircraft flies through is usually a moving body in relation to the earth(wind), and that accounts for the difference between ground speed and airspeed . $\endgroup$ – Mike Sowsun Mar 5 '16 at 0:48

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