Seagrass meadows derived from field to spaceborne earth observation at Midge Point, a coastal habitat in the central section of the Great Barrier Reef, September/October 2017

Seagrass meadow extent and meadow-scape was mapped using three alternative approaches at Midge Point, a coastal turbid water habitat, in the central section of the Great Barrier Reef, in September/October 2017. Approach 1 included mapping meadow boundaries and meadow-scape (including patches and scars) during low spring tides on foot within two sites (MP2 andMP3, each 5.5 hectare in area) using a handheld Garmin GPSMap 64s (accuracy ±1.5–3 m) on the 17 September 2017. Approach 2 was where the meadows were surveyed at low tide with observations from a helicopter (Robinson R44) on the 17 October 2017. The boundaries of the meadows were delineated by on-board observers and tracked by helicopter (at 25 ±5 m altitude) using the tracks setting on a handheld Garmin GPSMap 64s. Within these meadows, observational spot-check data was collected at an altitude of 1–2 m above the substrate, from three haphazard placements of a 0.25 m2 quadrat out the side of the helicopter at a number haphazardly scattered points (10 m2). Approach 3 used PlanetScope Dove imagery captured on 09 October 2017 coinciding as close as possible to the field-surveys, with 3.7 m x 3.7 m pixels (nadir viewing) acquired from the PlanetScope archive.