| A video camera system has been deployed in Bethany Beach, DE for the purpose of observing nearshore processes. The system captures several types of still images as well as video streams at regular intervals. The imagery can be used in the scientific analysis of coastal dynamics such as the prediction of rip currents or estimation of wave speed.; Multiple video streams are rectified and velocity fields are estimated using MatPIV, a MATLAB implementation of particle image velocimetry. The maximum velocity calculated at each point is assumed to be the local wave phase speed, and this value is used to calculate the local depth according to long wave theory. This bathymetry is compared to tide-corrected survey bathymetry to determine the accuracy of the depth-inversion.; The depth inversion appears to produce the best results when and where the incoming waves are either clearly visible and long-crested, or hardly visible at all. Uniform lighting appears to be ideal. In these regions, the calculated beach slope and depth match up with the survey bathymetry very well. Offshore, the inversion begins to fail possibly due to the diminishing visibility of the waves. Breaking waves and swash zone velocities produce false deep zones in the calculated bathymetry. Glare from the sun washes out the surface and movement cannot be accurately detected. Sunshine or clouds seem to not matter, as long as the sea surface is smooth and uniform. |
