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Abstract or Summary Between the 6th and 7th September, 2016, multispectral visible, red edge and near infrared images were acquired at a spatial resolution approximating 10 cm from a micasense sensor onboard a Swampfox X5 fixed wing RPA manufactured by Skycam UAV and subsequently an R44 helicopter to acquire imagery when the platform malfunctioned. The Swampfox RPA has a maximum all up weight of 4.7 kg and can carry a payload weighing up to 1.1 kg. The maximum flight duration is approximately 45 mins and the drone can cover over 200 ha in that time. The payload configuration consisted of a Sony NEX5 camera (red, green, blue) with 5 cm spatial resolution and a MicaSense RedEdge multispectral camera (red, green, blue, red edge, and near infrared) with 10 cm spatial resolution. Imagery was captured at a frame rate of 1 photo per 1.5 seconds concurrently with GPS (time, heading, location and altitude) and attitude data (pitch,roll and yaw). Flight lines ensured at least 75 % forward and side overlap, which enables a digital surface model (DSM) for each sensor to be produced through aerial triangulation and a block bundle adjustment (BBA). The DSM allows the retrieval of mangrove canopy height models (CHMs). Eight sites along the Wildman and West Alligator River were targeted, with these associated with areas experiencing significant colonisation by mangroves. Following observations of significant dieback, a second airborne overflight over the South Alligator and East Alligator Rivers, part of the West Alligator River and Field Island was undertaken on the 8th September, 2016, using a CESSNA, with colour photographs taken obliquely from both sides of the aircraft.
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