Roelfsema, Christiaan M; Saunders, Megan I; Canto, Robert Franklin C; Leon, Javier X; Phinn, Stuart R; Hamylton, Sarah (2014): Habitat Map for Lizard Island reef, Australia derived from a photo-transect survey field data collected in December 2011 and September/October 2012 [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.864209,

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Supplement to: Saunders, Megan I; Bayraktarov, Elisa; Roelfsema, Christiaan M; Leon, Javier X; Samper-Villarreal, Jimena; Phinn, Stuart R; Lovelock, Catherine E; Mumby, Peter John (2015): Spatial and temporal variability of seagrass at Lizard Island, Great Barrier Reef. Botanica Marina, 58(1), 35-49, https://doi.org/10.1515/bot-2014-0060

An object based image analysis approach (OBIA) was used to create a habitat map of the Lizard Reef.

Briefly, georeferenced dive and snorkel photo-transect surveys were conducted at different locations surrounding Lizard Island, Australia. For the surveys, a snorkeler or diver swam over the bottom at a depth of 1-2m in the lagoon, One Tree Beach and Research Station areas, and 7m depth in Watson's Bay, while taking photos of the benthos at a set height using a standard digital camera and towing a surface float GPS which was logging its track every five seconds. The camera lens provided a 1.0 m x 1.0 m footprint, at 0.5 m height above the benthos. Horizontal distance between photos was estimated by fin kicks, and corresponded to a surface distance of approximately 2.0 - 4.0 m.

Approximation of coordinates of each benthic photo was done based on the photo timestamp and GPS coordinate time stamp, using GPS Photo Link Software (www.geospatialexperts.com). Coordinates of each photo were interpolated by finding the gps coordinates that were logged at a set time before and after the photo was captured.

Dominant benthic or substrate cover type was assigned to each photo by placing 24 points random over each image using the Coral Point Count excel program (Kohler and Gill, 2006). Each point was then assigned a dominant cover type using a benthic cover type classification scheme containing nine first-level categories - seagrass high (>=70%), seagrass moderate (40-70%), seagrass low (<= 30%), coral, reef matrix, algae, rubble, rock and sand.

Benthic cover composition summaries of each photo were generated automatically in CPCe. The resulting benthic cover data for each photo was linked to GPS coordinates, saved as an ArcMap point shapefile, and projected to Universal Transverse Mercator WGS84 Zone 56 South.

The OBIA class assignment followed a hierarchical assignment based on membership rules with levels for "reef", "geomorphic zone" and "benthic community" (above).