2D local spectral information can be obtained form an image using Instantaneous Wavevector (IW). This 2D function is a vector quantity found by taking the gradient of the phase of the analytic image. Several synthetic images will be presented to illustrate the utility of IW analysis, and its application to OH airglow images will be discussed. The IW of an image gives us the dominant wavevector present at any point in the image. The amplitude of the analytic image gives us the magnitude of this component, and the phase differences of the analytic image between successive images allow us to infer the velocity of these waves. This method is used to determine phase velocities of internal waves from Hydroxyl airglow data. The instrument used, UWOSCR, is a scanning radiometer in the near infra-red, taking an 256 pixel image of the OH airglow every minute.