Considering the generation mechanisms of the atmospheric gravity waves and measurement techniques for TIDs
, some useful rules for explaination of the measurements are drawn. It is shown that: TIDs
consist of two harmonic waves which are orthogonal to each other, and both the measurement techniques for TIDs
i.e. the total electron content measurement and the electron density measurement are equally effective. Accordingly inversion formulas for determination of the phase velocity of TIDs
from radio astronomical data are derived, and the suppressing effects on wave amplitude are discussed.