Originally Posted by BOAC
Whatever 'high-fallutin' references you come up with, GROUND speed is ALWAYS speed relative to the ground.
Yes, well, whatever that means precisely.
If high-falutin' is too rarified, let's take the low-falutin' route.
Consider. The earth is a perfect sphere, with circumference about 21,600nm (if we take a nm to be a second of arc, which is what it was supposed to be). You fly at your preferred altitude of FL370, let's say in a standard atmosphere. I fly at 1,000 ft because I like to bird-watch. Both of us without wind (we should be so lucky!). We are both pretty fast - say we go around the earth in a day. Just under 1,000 kts per (let's not worry about the logistics of refuelling, or about the number of windows shattered in my wake).
But you are about 6 nm higher than I (1 nm is about 6,000 ft) so you actually travel 21,637.7 nm, whereas I travel 21,601 nm. You do nearly 37 more air miles than I! So your TAS is about 1.5 kts faster than mine.
Those NASA "muppets" (as PA dubbed them) says your ground speed is 1.5 kts faster than mine. Myron Kayton says that also. What do you say?
PBL