ATCast, I'm glad it helped answer your question!
PA, if you are asking me to scan the Figure in, I would rather suggest looking at the entire Sections 2.2-2.4, pp 23-32, because they also include the equations of motion associated with the quantities in the diagram.
amazon.com (the US branch; local country branches of amazon might be different) has scanned the book, and if you have an account with them, you can search it. The relevant sections in Chapter 2, The Navigation Equations, are 2.2 Geometry of the Earth; 2.3 Coordinate Frames; 2.4 Dead-Reckoning Computations.
Concerning Gratton's paper; yes, it is not nav, but he calculates true airspeed using vector triangles in a way that is only correct if ground velocity is taken to be the the horizontal component of the resultant of the air velocity vector with the wind vector (where by "horizontal" I mean in a plane parallel to the tangential plane of the reference ellipsoid). So that is indirect confirmation, even though not explicit definition.
Checkboard, Kayton and Fried is a canonical reference; I am not really anonymous; and I suggest you may rely on my interpretation.
PBL