The Global TanDEM-X High-Resolution Coastline Product

Abstract. We present a globally consistent, high-resolution (10 m) coastline product derived from the TanDEM-X DEM product of the German SAR satellite mission TanDEM-X (DOI: 10.15489/entfdgi5es81). This vector product was developed with the aim of refining the TanDEM-X DEM, ensuring an optimal fit with this dataset. Additionally, the TanDEM-X coastline is a key component for deriving hydrographic data in the project HydroSHEDS v2.0 and thus defines the outer boundary of watersheds and rivers. To meet hydrological requirements, the TanDEM-X coastline was first extracted automatically and subsequently manually verified and improved. Since the coastline is a mapping feature located in the coastal zone, its position depends on the source data, the method used to identify the coastline, the time of acquisition, and the purpose of mapping. Due to this complex process and the lack of true reference data, a validation of the coastline product is challenging. Therefore, the quality of the TanDEM-X coastline is evaluated through statistical and qualitative comparisons in different globally distributed coastal areas and against multiple existing coastline products.