The Chordline midpoint is a characteristic of an Airfoil. It is the point that is on the chordline, half way between the leading edge and the trailing edge. The figure below illustrates the location of the chordline midpoint for a given airfoil.

Note: if there are no structural offsets (see Blade structure file) or prebends (see Blade shape file), the chordline midpoint is on the pitch axis, as in the figure above.