Accuracy Assessment for the Reclassification of the NOAA Florida Keys mapping

This report describes the methodologies, analyses, and results for an independent accuracy assessment of a thematic benthic habitat map produced by NOAA for the Lower Florida Keys. It is a reanalysis of a previous accuracy assessment for a different classification scheme. Over the course of the Florida Keys mapping project, NOAA amended part of the classification scheme. The original scheme for mapping benthic cover was a tiered approached where certain benthic cover categories were given priority over others (e.g. coral was most important). Recently, this was modified to a dominant benthic cover scheme where the habitat is characterized by the single most dominant cover type and all habitats are characterized for percent cover of coral. No new data were collected for this effort. The exact same data and data analyses from Walker and Foster (2010) were used to evaluate the accuracy of the reclassified map. The same analyses are currently underway for accuracy assessment area 1 from Walker and Foster (2009). The accuracy assessment was conducted within a 249.6 km² corridor (ROI-2) between Sand Key and Eastern Sambo that extended from the shoreline intertidal zone, through Hawk Channel and the reef tract, before terminating on the outer bank/shelf escarpment at a depth of approximately 33m. A total of 533 sampling stations were visited, of which 476 were used in the accuracy assessment. The sites were selected using a stratified random sampling protocol that equally distributed sampling points amongst the detailed structure categories. Most sites were sampled by deploying a weighted drop camera with the vessel drifting in idle and recording 30-120 seconds of dGPS-referenced video. The shallowest sites were sampled by snorkel, waverunner, or kayak, using a hand-held dGPS for navigation and a housed camera to record video. Each sampling station was given a Detailed Structure and Biological Cover assignment in the field. These field classifications were reevaluated post-survey during a systematic review of video and photographic data, designed to ensure consistency within classifications. The efficacy of the benthic habitat map was assessed by a number of classification metrics derived from error matrices of the Major and Detailed levels of Geomorphological Structure and Biological Cover. The overall, producer's, and user's accuracies were computed directly from the error matrices. The overall accuracy of the ROI-2 benthic habitat map was 89.3% and 83.2% at the Major and Detailed levels of Structure respectively, and 85.5% and 73.1% at the Major and Detailed levels …