Automation of coastline detection

Coastline monitoring from video average images enables to assess erosion/accretion processes of a beach. Multiple calculation methods exist. Nevertheless, they often lack robustness to make it operational. To cope with this issue, Waves’n see has developed a technique of coastline’s automated detection, adapted to each study site. It is based on image segmentation by artificial intelligence and by k-means method. Then, a statistical analysis of coastline’s position maximizes the calculations’ confidence. This new methodology enables not only automated calculations, but also a coastline detection at least three times more efficient. In concrete terms, valid coastlines used to be obtained on 20 to 30% of images, whereas they are now obtained […]

Image stabilization

Video monitoring of coastal processes can be disturbed by camera movements. Whereas wind gust can cause high frequency movements, thermal dilation of the structure on which the camera sits on may cause daily frequency movements (see figure below). Horizon line position, characterized by a daily signal. In order to make a scientific use of our 4K images and videos (monitoring of coastline, beach topography, waves, bathymetry), we have developed and adapted image stabilization techniques to our needs. Two main cases are distinguished. In the first one, fixed elements in the image like windows and buildings edges are used as landmarks to register an image to an other. An improved version […]

How is your beach doing ?

From topographies generated by Wavecams technology, Waves’n see establishes diagnostics revealing the health state of a beach, by measuring the erosion during stormy events, and the accretion during the following recharges. First, a straightforward approach consists in extracting topography at points of interest, located for example in the upper/lower part of a beach, and on each sides of a groyne, in order to evaluate the different erosion and accretion phases. Then, in order to assess alongshore and cross-shore sediment transport, a joint analysis of topography evolution along transects (cross-shore and along-shore) is carried out. At a larger scale, global statistics of topography (mean height, successive height and volume difference, cumulative […]

Wavecams topography validation

Wavecams topographies are validated by comparison with independent topography measurements: DGPS and Lidar data if available. Here is an example of validation with DGPS measurements acquired in the central part of Etretat bay on the 10th of January 2020, through the following 3D interactive figure (to move inside the figure: left clic(rotation), mouse wheel( zoom), right clic(translation)) : After interpolation of DGPS data on our topography grid, we obtain very good validation results: MAE=27cm, RMSE=32cm (MAE: Mean average Error, RMSE: Root Mean Square Error) Here is an example of validation with Lidar measurements acquired in the whole Etretat bay on the 28th of August 2019, through the following 3D interactive […]

Beach topography overview

Monitoring of beach topography evolution on any tidal area is made possible by Wavecams technology. It enables to efficiently retrieve not only seasonal erosion or accretion trends, but also high frequency topography evolution (about 2 to 4 weeks) emphasising for example the erosion caused by a storm and the subsequent beach recharge. For example, both quarterly and monthly beach topography evolutions in the center part of Etretat bay have been computed: The effect of major storm events in December 2019 and January 2020 is clearly visible. Beyond this very visual first approach, the characterization of topography evolutions can be quantitatively and precisely done through adapted diagnostics. This will be tackled […]