Capability of Planet Dove for monitoring the world's coastlines

Coastal ecosystems worldwide are increasingly threatened by the impacts of climate and land use change, which alter habitat structure, disrupt ecological processes, and reduce ecosystem resilience. Satellite imagery provides an important tool for monitoring these changes and informing scientists and policymakers. However, coastal systems are extremely dynamic in space and time, and many fine-scale processes and short-lived events are missed by satellites that provide resolutions coarser than 10 m with multiday revisit times, e.g., Landsat and Sentinel-2. Commercial satellites have historically offered higher spatial resolution, and the emergence of large constellations has enabled a shift toward more systematic global coverage. The Planet Dove constellation combines 3 m spatial resolution with near-daily acquisition, creating a large archive of repeated meter-scale observations of coastal environments. Here, we provided practical insights into the opportunities and limitations of using Planet Dove (PlanetScope) imagery in coastal environments by analyzing global coastal image availability. Within 20 km of the world's coastlines, the Planet Dove archive contains over 100 million images between 2014 and 2024. From 2016 to 2024, considering mostly clear imagery (≥75% clear), each global coastal region was imaged on average 516 times. Of these areas, 6.2% of grid cells had a median revisit of 1 day, 63.6% had a revisit interval of 7 days or less, and 87.5% had a revisit interval of 30 days or less. We examined the implications of these revisit times for tidal observations and found large amounts of spatial variability in tidal coverage provided by Planet Dove. In some areas, the archive imaged nearly the full tidal range and maintained ~weekly revisit times for a given tidal stage. By contrast, certain regions, such as portions of South America and Australia, captured only one tidal mode, and others, such as Alaska, experienced much longer revisit times (e.g., > 3 months) when tidal conditions were controlled for. These results show that a high volume of imagery does not necessarily translate into improved monitoring capability, as the timing and environmental context of observations can determine their suitability for a given application. The spatial and temporal coverage provided by Planet Dove is particularly useful for monitoring short lived coastal processes (e.g., nearshore sediment plumes), mapping small and fragmented coastal habitats, and monitoring applications where controlling for tidal variability is important. However, issues with sensor calibration, geometric quality, and data cost have limited the development of standardized high resolution data products on continental to global scales.