# What is the name of centre of mass speed of an aircraft?

I have a list of positions (X [NM], Y[NM], Z[NM]) of an aircraft. Every coordinate is given every 1 second.

I calculate the speed [knots] between two consecutive coordinates in the following way:

$S_{i+1}=\frac{\sqrt{(X_{i+1}-X_{i})^2 + (Y_{i+1}-Y_{i})^2 + (Z_{i+1}-Z_{i})^2}}{1s}3600\frac{s}{h}$

It's basically space over time.

Does this 3D speed have a specific name?

• That's a trippy question :) – Koyovis Nov 24 '17 at 13:49
• I dunno what you are trying to solve for there. Yeah, technically it would solve for velocity, but I don’t know where such a calculation would be used in aviation. – Carlo Felicione Nov 24 '17 at 14:09
• I don't want to try to solve anything... I just wonder if such speed has a specific name... it seems to me strange that there are definitions for ground speed, airspeed and so on but no definition for what I consider the most intuitive and basic definition an aircraft can have... – Federico Gentile Nov 24 '17 at 15:26
• How is this not instantaneous ground speed ? – Jeffrey Nov 24 '17 at 16:26
• Ground speed does not have the z-axis – Koyovis Nov 25 '17 at 11:00