Beach surface model construction: A strategy approach with structure from motion - multi-view stereo.

In contrast to traditional beach profiling methods like topographic surveys and GNSS, which pose significant challenges in terms of cost and time, this research underscores the efficiency, cost-effectiveness, and simplicity of terrestrial photogrammetry employing the Structure from Motion-Multi View Stereo (SfM-MVS) method. Notably, this approach enables the utilization of commonplace devices such as smartphones for data capture. The methodology integrates a 12-megapixel camera for image acquisition, processed through Agisoft Metashape Professional software, and validated for accuracy using ground control points (GCPs) and checkpoints (CKPs) calibrated via GNSS. Findings reveal substantial disparities in positional accuracy according to the Ground Control Points distribution. The study underscores the critical role of strategically distributing GCPs and CKPs in effectively mapping coastal areas, thus affirming the potential of SfM-MVS as a powerful and accessible tool for coastal monitoring initiatives. This research contributes significantly to advancing the efficiency and accessibility of beach profile monitoring, offering invaluable insights for researchers and practitioners in coastal management and environmental conservation efforts.•A simplified beach profile modeling methodology is proposed.•The method is faster and more cost-effective than traditional surveys (RTK GNSS, lidar, RPA).•The study highlights the importance of GCP and CKP distribution in enhancing SfM-MVS accuracy for coastal mapping.

The dynamics of plastic pellets on sandy beaches: A new methodological approach.

Plastic found in the coastal zone is a result of waste mismanagement. This material comes directly from offshore disposal or by fishing debris, other marine activities, and by marine currents and winds, as well as urban drainage systems and estuaries. Specifically, in the case of plastic pellets, which are spheres with 2-5 mm that constitute the raw material for the manufacture of plastic products, the Santos Port and the plastic factories in Cubatão city (Brazilian southeastern coast), are considered the main local sources for the São Paulo state coast. Consequently, the beaches most affected by this pollutant are those near Santos estuary, like Enseada do Guarujá beach. However, some questions are still open, such as: what are the mechanisms which control the pellets deposition, and which locations are most favorable for deposition on the beach? To answer these questions, a four-step research was carried out at Enseada beach: 1) Plastic pellets geodetic survey based on GNSS positioning; 2) Beach geomorphometric parameters (altitude, aspect, and slope) derived by Digital Elevation Model (DEM); 3) Strandline altitude estimated through wave climate and tide height; and, 4) Plastic pellets deposition Suitability Index (PSI). The joint analysis of the altimetric, geomorphometric and meteoceanographic aspects showed that the beach areas with altitudes higher than those calculated for the strandline (>2.06 m), slope ~ 3° and facing the same direction of the higher energy waves (157.5-202.5°) were more susceptible to pellet deposition. This indicates that the accumulation of this pollutant on the beach is controlled not only by its physical characteristics, but mainly by storm surge events. Besides, surveys with geodetic reference (fixed, univocal, and relatively stable on time) bring up altimetric information as a result of all interactions and can be compared with other beaches anywhere on the planet - thus contributing to a standardization of the survey methodology.