Recent developments in satellite processing tools allow low-cost, fast and automatic processing of a large amount of information from Earth observation, enhancing the capability of detecting coastal changes from space at different temporal scales. Some works have assessed the quality of these data and applied it to detect coastal evolution locally, most of them focusing on mid-term and long-term changes in the coastline. In this work, we evaluate the capability to monitor changes in coastal morphology at various temporal and spatial scales using 1D (coastlines) and 3D (bathymetry) satellite-derived data obtained from site-specific processing methods. Local characteristics were included in several phases of the development of the satellite products used here: i) geolocated very high resolution images from each pilot site were used in the coregistration process to enhance geolocation accuracy in images from different missions, ii) different spectral indices were tested at each pilot site to obtain more reliable detection of the coastline at all sites and iii) measured topobathymetry data were used to obtain datum-based satellite shorelines and bathymetry. The accuracy and skill of those satellite products were assessed at several pilot sites in Spain. The results indicated high horizontal accuracy (RMSE < pixel size), with errors on the order of half of the pixel size (RMSE = 5.0 m and for Sentinel-2 and 18.8 m for Landsat5). Furthermore, the coastlines used here presented errors comparable to those obtained from the widely used open-source tool CoastSat. Time-series analysis using satellite-derived shorelines showed that coastal change processes can be detected at several temporal and spatial scales, such as short-term erosion and accretion events on a small beach, seasonal beach rotation, and long-term trends at local and regional scales. However, the results from satellite-derived bathymetry indicated that the quantitative assessment of the coastal morphology with 3D products is still limited. Some in situ measurements are necessary to obtain satellite data that represent site-specific conditions. However, the quantity of this auxiliary in situ measurements required to obtain reliable time series of satellite derived shorelines and bathymetry is significantly lower than the quantity required by traditional monitoring methods. The results are discussed, highlighting the gaps that need to be filled in the future so that satellite-derived products can be used in usual coastal change monitoring practices.

中文翻译：

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论利用卫星信息探测海岸变化：西班牙海岸示范案例

卫星处理工具的最新发展使得能够低成本、快速、自动地处理来自地球观测的大量信息，增强从空间检测不同时间尺度海岸变化的能力。一些工作评估了这些数据的质量，并将其应用于当地检测海岸演化，其中大多数关注海岸线的中长期变化。在这项工作中，我们使用从特定地点的处理方法获得的 1D（海岸线）和 3D（测深）卫星数据来评估监测不同时间和空间尺度的海岸形态变化的能力。这里使用的卫星产品开发的几个阶段都包含了当地特征：i）在配准过程中使用来自每个试点的地理定位超高分辨率图像，以提高来自不同任务的图像的地理定位精度，ii）不同的光谱指数iii) 使用测得的地形测深数据来获取基于基准的卫星海岸线和测深数据。这些卫星产品的准确性和技能在西班牙的几个试点地点进行了评估。结果表明水平精度较高（RMSE < 像素大小），误差约为像素大小的一半（Sentinel-2 的 RMSE = 5.0 m，Landsat5 的 RMSE = 18.8 m）。此外，这里使用的海岸线所呈现的误差与从广泛使用的开源工具 CoastSat 获得的误差相当。使用卫星海岸线进行的时间序列分析表明，可以在多个时间和空间尺度上检测海岸变化过程，例如小海滩上的短期侵蚀和吸积事件、季节性海滩旋转以及当地和地区的长期趋势。区域尺度。然而，卫星测深结果表明，利用3D产品对海岸形态进行定量评估仍然有限。为了获得代表特定地点条件的卫星数据，需要进行一些现场测量。然而，获得卫星海岸线和水深测量的可靠时间序列所需的辅助现场测量数量明显低于传统监测方法所需的数量。对结果进行了讨论，强调了未来需要填补的空白，以便卫星衍生产品可以用于通常的沿海变化监测实践。