From the 2011 LiDAR data, mangroves occurring on Field Island and all four rivers (including the East Alligator) were associated with areas where the vegetation CHM value was equal to or exceeded 0.5 m. This threshold selected as approximately 95% and 97% of the area of mangroves mapped from AP and CASI, respectively (and remaining relatively unchanged in the intervening years) was captured. This threshold was also considered to be above the noise levels commonly associated with LiDAR data. As with the AP, and with reference to these data, the classification was manually adjusted to ensure that there was minimal confusion with known areas of other cover types (e.g., saltmarsh, sediments, and coastal woodlands/shrublands).
Extent Data Link https://dap.tern.org.au/thredds/catalog/landscapes/remote_sensing/mangroves/Kakadu_NP/Mangrove_Extent_Maps/2011_Extent_LIDAR/catalog.html
As neither finer spatial resolution airborne nor field data were acquired at the time of the airborne LIDAR acquisitions, the accuracies of the classifications could not be easily quantified. However, the refinement through visual interpretation provided a high level of confidence in the maps of mangroves derived from the LiDAR data. However, to indicate the accuracy of the refined classification, 400 segments were randomly chosen and their assignment was assessed visually against interpretations of the original data. The overall accuracy in LIDAR-based classification was 95% for mangrove and non mangrove (e.g., saltmarsh and sediment).
References Asbridge, E. and Lucas, R.M. (2016). Mangrove response to environmental change in Kakadu National Park, Australia. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing (IEEE JSTARS), 9, 5612-5620.
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