National Network of Regional Coastal Monitoring Programmes


EO-TWL is an Earth Observation enabled method for mapping intertidal elevations. The tool is based on original research led by Dr Paul Bell, using the 'Temporal Waterline Approach' (TWL) to map intertidal topography using X-Band Marine Radar (see references below). The X-Band radar approach has since been licenced and developed into a commercial service provided by Marlan Maritime Ltd.

Since c. 2018, via a series of NERC and ESA funded projects, the X-Band TWL algorithms and workflows have been further developed to exploit the capabilities of the ESA Sentinel satellites, this approach is referred to as EO-TWL. The use of satellite data transforms the spatial and temporal capabilities of the method enabling the potential for routine large-scale intertidal monitoring.

The current project is focused on three main tasks:

  • making the code and workflow computationally efficient,
  • ensuring the code is re-usable and maintainable, and;
  • addressing the needs of the user communities that benefit from access to the information delivered by EO-TWL, including peer-review publication of the method.

Processor overview

The flowchart below provides an overview of the EO-TWL processing chain, which uses Sentinel 1 and Sentinel 2 data coupled with accurate information on water levels to derive elevations via a correlation process.

Key References:

  • Bell P.S., Bird C.O & Plater A.J., 2015, A temporal waterline approach to mapping intertidal areas using marine X-band radar. Coastal Engineering, Volume 107, January 2016, Pages 84–101. DOI:10.1016/j.coastaleng.2015.09.009
  • Bird, Cai O.; Bell, Paul S.; Plater, Andrew J..2017 Application of marine radar to monitoring seasonal and event-based changes in intertidal morphology. Geomorphology, 285. DOI: 1-15.10.1016/j.geomorph.2017.02.002
  • Mason, D., Davenport, I., Robinson, G.J., Flather, R.A., McCartney, B.S., 1995. Construction of an inter-tidal digital elevation model by the “water-line” method. Geophysics Research Letters, 22:3187–3190.

Funded projects that have supported the development of EO-TWL:

Access to demonstration datasets: [Coming Soon]