VIDEO ESTIMATION OF SUBAERIAL BEACH PROFILES

A technique is presented that allows estimation of the subaerial beach profile using video imagery. Using either a shadow from a pole or the light from a narrow slit, a line can be "drawn" across the beach at a known origin and angle. When viewed from the longshore direction, the line will appear as a visible beach profile that can be digitized from the image and the ground coordinates of the profile uniquely determined. The theoretical pixel vertical footprint is about one thousandth of the range from the camera, or, for a typical camera, about 10 cm at the 100 m range. Accuracies can be up to +/- 1/2 pixel, or +/- 5 cm at this range. A field test, using a fire hose as a proxy for the shadow, proved the technique, with an average accuracy of +/- 68% of the theoretical footprint size being found. The success of this technique suggests that profile data may be routinely collected using an automated system without the need for a survey team, thus allowing the ready collection of long time series for climatological studies.