The word dopplergraph is a combination of the words doppler  and photograph . Just as a photograph is a two-dimensional record of variations in light intensity, a dopplergraph is a two dimensional record of variations in the doppler shift in light intensity. In fact, a dopplergraph need not be a record of the shift of visible light, but of any radiated wave, which includes electromagetic waves and acoustic waves. Since the doppler shift is caused by the velocity of the radiating source towards or away from the viewer, a dopplergraph is a picture of the velocities associated with the sources being viewed.