BACKGROUND AND OBJECTIVES: Coastal zones represent dynamic interfaces where terrestrial and marine spaces meet, often creating challenges for governance, spatial planning, and cadastral clarity. In Bekasi Regency, the absence of a unified reference line between land and sea has led to overlapping jurisdictions, uncertain land tenure, and difficulties in implementing integrated coastal management. The study objectives were to establish a legal coastline based on the high-water spring datum as a unifying framework for land and marine cadastre, ensuring compliance with International Hydrographic Organization S-4 and C-13 standards and Indonesian Law Number: 32/2004 on coastal zone governance.METHODS: The research combined long-term tidal data from Muara Bendera, unmanned aerial vehicle based orthophotos, high-resolution digital elevation model extraction, and global navigation satellite system surveys to delineate the High-Water Spring shoreline. Unmanned aerial vehicle images were collected at both high and low tide to capture the full range of shoreline positions, while real time kinematic measurements provided precise ground control for validation. The shoreline was then adjusted to the high-water spring vertical datum in accordance with International Hydrographic Organization guidelines, and cross-validated across different coastal morphologies, including sandy beaches and mangrove-lined areas.FINDINGS: Unmanned aerial vehicle mapping achieved strong performance on sandy coasts (Muara Beting: mean positional error 2.06 meters, overall validation score 75.6/100) but struggled in mangrove-dominated areas (Muara Bendera: mean error 34.63 meters, score 37.7/100), demonstrating the importance of RTK ground validation in complex coastal environments. Despite these differences, the integrated workflow successfully produced a continuous high-water spring-based coastline for Bekasi Regency that aligns with both scientific and legal standards.CONCLUSION: The study concludes that adopting a high-water spring based legal coastline provides a stable and authoritative boundary to unify land and marine cadastre. It not only resolves spatial overlaps but also strengthens the foundation for administrative governance, spatial planning, and coastal zone management. While unmanned aerial vehicle photogrammetry offers a practical solution for sandy coast, mangrove environments require hybrid approaches combining remote sensing and ground surveys.
Setiyadi et al. (Thu,) studied this question.