Abstract: Systems and methods for determining the speed of a vessel from an overhead image of the vessel's wake can include the initial step of defining a cusp line for the wake. A representative line segment from the defined cusp line that is suitable for building an image intensity profile for the image can be selected. Once the intensity profile is built along the line segment, the wake wavelength ?cusp from the image intensity profile can be found by measuring the distance between successive points of intensity maxima (or successive intensity minima points) along the line segment. Once ?cusp is found, the vessel speed can be determined from the images according to the formula ?ship=?{square root over (1.352*?cusp)}. The systems and methods can be practiced using any overhead imagery systems that display a vessel's wake, including synthetic aperture radar (SAR) and electro-optical (EO) overhead imagery systems.