Computing Vessel Velocity from Single Perspective Projection Images

Abstract

The Master’s Thesis presented an image-based approach to estimate the speed of moving vessels from their traces on the water surface. Vessels moving at constant heading and speed display a familiar V-shaped pattern which only differs from one to another by the wavelength of their transverse and divergent components. Such wavelength is related to vessel speed. We use planar homography and natural constraints on the geometry of ships’ wake troughs to compute vessel speed from single optical images acquired by conventional cameras. Experiments show that our approach produces compelling results, which are in accordance with true data available for the observed vessels.

Using Conventional Cameras as Sensors for Estimating Confidence Intervals for the Speed of Vessels from Single Images

“…For instance, notice in Figure 1 that the horizon line would be behind the mountains. For the RANSAC-based technique that was used by Huillca and Fernandes [13], on the other hand, the horizon line between the sky and the water must be visible because it is detected as the most apparent straight line in the edge image.…”

“…Huillca and Fernandes [13] took the point samples for one of the wave arms and followed a naive approach that used a Savitzky-Golay filter [24] for curve fitting. They performed both procedures in the rectified image of the ROI.…”

“…In a recent study, Huillca and Fernandes [13] presented a semi-automatic method to calculate the speed of a vessel directly from one image that was acquired by a conventional camera. The method is based on projective geometry and estimates vessel speed from an analysis of the Kelvin wake pattern.…”

“…The inverse ship wake problem consists of estimating parameters, such as speed, from the observation of wake patterns [15]. The approach that was proposed by Huillca and Fernandes [13] detects features (crests or troughs) of the extracted wave arm and applies the inverse ship wake problem to estimate the speed of the corresponding vessel. However, the technique requires the horizon line to be visible in the image.…”

“…This paper presents an extended version of the approach that was proposed by Huillca and Fernandes [13]. The extension included the automatic estimation of the vanishing line, a different approach to identifying the wave arms, the use of the troughs in the closest wave arm to estimate the wavelength, the use of radar to validate the results, the estimation of confidence intervals for the measurements, and the analysis of error propagation throughout the computational chain.…”