Shoreline position (Balearic Islands, Spain)

Instantaneous shoreline position dataset from in-situ RTK-GNSS measurements, land-based beach imaging systems and optical remote sensing platforms The Shoreline product provides time series of instantaneous shoreline positions from five microtidal beaches in the Balearic Islands (Spain), obtained from different observation platforms and using different shoreline extraction methods. The dataset integrates RTK-GPS measurements, shorelines derived from land-based remote sensing platforms (SIRENA and CoastSnap), and multispectral satellite imagery. A total of 3745 shorelines are included in the product. Technical details The dataset is provided as an ESRI Shapefile containing multipointZ (XYZ) shoreline geometries in WGS84 coordinates, with orthometric heights referenced to the Alicante Mean Sea Level (NMMA) datum. Each feature -with a unique identifier- represents a shoreline at a specific time, location, and extraction method. An accompanying JSON file provides CF-compliant metadata and explanations of the variables. The product integrates three methodological sub-datasets: In-situ & Manual Beach-Imaging: RTK-GPS surveys and manually digitized shorelines from fixed coastal video stations (SIRENA) and citizen-science camera cradles (CoastSnap). Satellite-Derived Shorelines (SDS): Automated waterline extractions from Sentinel-2 and Landsat 8/9 imagery using deep-learning models within the CoastSat pipeline (https://github.com/kvos/CoastSat/). AI-Driven Beach-Imaging Shorelines: Automated shoreline extractions from coastal imagery using CNN-based semantic segmentation (https://github.com/ai4os-hub/socib-shoreline-extraction). Except for the RTK-GPS data, for which each measured point has its corresponding Z value, image and satellite-derived shorelines were assigned a single elevation value, based on the sea-level value from the Puertos del Estado tide gauge closest in both time and space. Sea-level values were referenced to the Alicante Mean Sea Level (NMMA), Spanish datum, and reconstructed using the ttide code. Parameters This product includes shorelines collected at multiple sites using various observation platforms and extraction or acquisition methods. The parameters included in the dataset to distinguish between these different characteristics are listed below. Variable Long Name Units Y latitude degree_north X longitude degree_east Z altitude / geometric height above the geoid m ID unique shoreline identifier dimensionless TIME UTC time YYYY-MM-DDTHH:MM:SSZ PLTF_N platform name / site dimensionless PLTF_ID platform id / observation platform type dimensionless METHOD shoreline extraction method dimensionless QC quality_flag dimensionless Data sources Platforms: human; Landsat-8; Landsat-9; Sentinel-2; CoastSnap and SIRENA video-monitoring stations managed by the Balearic Islands Coastal Observing and Forecasting System (SOCIB). Instruments: Leica GS10 RTK-GNSS; GEOMAX Zenith60 RTK-GNSS; red de mareógrafos (REDMAR) de Puertos del Estado. Data quality RTK-GNSS-derived shorelines: Accuracy and quality depend on instrument specifications and manual data cleaning. Instrumentation undergoes regular maintenance, and data processing is performed by qualified personnel following quality control procedures. The approximate horizontal and vertical positional accuracy within ±0.05 m. Image-derived shorelines (manual digitization): Accuracy is assessed by direct comparison with simultaneous RTK-GPS measurements, focusing on the cross-shore component using distance-based metrics. Accuracy varies depending on the site, imaging system, and distance from the camera. Overall, the approximate Root Mean Square Distance (RMSD) ranges between 1 and 3 m for microtidal sites. Satellite-derived shorelines: Accuracy was assessed against concurrent (±24 h) RTK-GPS and manually digitized shorelines. Both Sentinel-2 and Landsat 8/9 achieved sub-pixel accuracy, with RMSD values of approximately 4–8 m for Sentinel-2 and 11–13 m for Landsat 8/9 within the CoastSat pipeline (regionally self-trained models). AI-derived image shorelines: Accuracy is assessed against manually digitized shorelines, with MAD values ranging from 2.6 to 3.4 m, approaching the uncertainty associated with expert manual digitization. Spatial and Temporal coverage Site Longitude Range Latitude Range Elevation Range Time Period Number of shorelines Cala Millor 3.3845 to 3.3870 39.5877 to 39.6035 -0.72 m to +1.34 m 2013-04-09T08:32:04Z to 2025-07-10T14:51:28Z 913 Son Bou 4.0537 to 4.0786 39.8957 to 39.9076 -0.64 m to +1.58 m 2011-10-22T11:00:00Z to 2025-10-14T09:54:35Z 692 Muro 3.1168 to 3.1215 39.8017 to 39.8176 -0.57 m to +0.59 m 2013-04-09T08:32:04Z to 2026-03-18T10:33:28Z 917 Samarador 3.1851 to 3.1864 39.3492 to 39.3504 -0.26 m to +1.67 m 2022-07-21T06:45:00Z to 2025-10-08T11:36:45Z 265 Arenaldentem 2.9742 to 2.9913 39.3341 to 39.3531 -0.48 m to +1.99 m 2013-05-11T08:26:59Z to 2025-10-08T13:03:11Z 958 Contact information For further technical inquiries or additional information about the dataset, please contact [e-mail] Related works Oliver-Sansó, J., Soriano-González, J., Varona, J., Moyà-Alcover, G., Sánchez-García, E. (2026). Automating shoreline extraction from beach imaging systems for coastal monitoring. Environmental Modelling & Software, 107078, https://doi.org/10.1016/j.envsoft.2026.107078. González-Villanueva, R., Soriano-González, J., Alejo, I., Criado-Sudau, F., Plomaritis, T., Fernàndez-Mora, À., Benavente, J., Del Río, L., Nombela, M. Á., and Sánchez-García, E. (2023). SCShores: a comprehensive shoreline dataset of Spanish sandy beaches from a citizen-science monitoring programme, Earth Syst. Sci. Data, 15, 4613–4629, https://doi.org/10.5194/essd-15-4613-2023.