Mapping ebb tidal delta dynamics using Planet cubesat imagery within the Google Earth Engine Journal Paper
- Author
- Ford, M.R.; Dickson, M.E.; Durrant, T.H.
- Year
- 2021
- Journal / Source
- Australasian Coasts & Ports 2021 Conference
- Pages
- 424-428
- Summary
- The recent development of relatively low-cost Earth observation satellites now provides the ability to image the entire Earth’s surface at daily timescales. Such high-cadence imagery has unlocked the ability to examine a range of processes at spatial and temporal scales previously inaccessible within coastal science. Here we present details on the use of imagery from the Planet Labs constellation of Earth observation satellites to examine changes on the Whāingaroa (Raglan) Harbour ebb tidal delta on the west coast of the North Island of New Zealand. The time-averaging of stacks of still images captured by oblique land-based cameras has been widely used to identify features such as rip channels, nearshore bars, ebb-tidal delta bars and channels, among others. Recently, a similar method has been developed to work with collections of satellite imagery from a range of government and commercial satellite sensors. By accessing 194 cloud-free images from 2017- 2019 we are able to time-average collections of Planet Labs imagery with the Google Earth Engine (GEE), a cloud-based geospatial analytics platform. Using this approach, we can quantify the migration of bars and the main channel at the Raglan ebb tidal delta. Additionally, outputs of a high-resolution (5 km) wave hindcast of New Zealand waters and local tidal predictions were used to determine the wave conditions and water level at the time each image was captured enabling us to examine tidal and wave control on patterns of wave breaking. The approach we use is simple and with the growing constellations of commercial and government Earth observation satellites has a range of potential applications within coastal dynamics and maritime safety.