A review of the data was conducted in three phases: 1) an on-line review to ensure attribute completeness with comparison to the ecologists' delineations; 2) a review of 1:48,000 scale maps of the compiled data against the original source photos; and 3) a review of 1:24,000 scale maps of the compiled data against the original delineated photographs for attributes.
Ground truthing was conducted to verify that benthic habitats seen in the water were properly identified on aerial photographs. Researchers were able to conduct most ground truthing of benthic communities while snorkeling. SCUBA was used for those communities located in deeper water habitats or turbid water. Field information about the benthic habitat and site GPS locations were recorded. The completed photos were reviewed for content and accuracy by the ecologists and Florida Marine Research Institute (FMRI) staff and then sent to NOAA for digital compilation.
Natural color aerial photographs of the Florida Keys region were acquired by NOAA's Remote Sensing Division during overflights occurring from December 1991 through March 1992. A Wild RC-30 camera mounted in a Cessna Citation II Fanjet aircraft was used. The source photography was at a nominal photo scale of 1:48,000 (1 cm = 480 m). Each photograph covered an area of approximately 160 km 2 . An 80-percent endlap and 60-percent sidelap between adjacent photographs ensured both complete coverage and the presence of adequate reference locations necessary for determining positional accuracy. Approximately 450 photos provided monoscopic coverage and were used to delineate benthic habitats.
Establishing a Habitat Classification Scheme:
Two recognized ecologists, both with local knowledge of the Florida Keys and extensive expertise in marine habitats, were responsible for interpreting and delineating the benthic communities seen on the aerial photographs. These two ecologists, along with Florida Marine Research Institute (FMRI) staff, developed the hierarchical classification scheme used in this atlas. The habitat classification scheme is composed of 24 classes of benthic communities in four major habitat categories: corals, seagrasses, hardbottom, and bare substrate. Special modifiers were attached to the classes to denote dredge zones, banks, and restoration areas.
Photointerpretation:
The ecologists and Florida Marine Research Institute (FMRI) staff interpreted and then delineated benthic habitats on the aerial photos. The minimum habitat area delineated was 0.5 ha. Because of their ecological significance as critical habitat in the Florida Keys, patch reefs of less than 0.5 ha were delineated as a dot. Ground truthing was conducted to verify that benthic habitats seen in the water were properly identified on aerial photographs. Researchers were able to conduct most ground truthing of benthic communities while snorkeling. SCUBA was used for those communities located in deeper water habitats or turbid water. Field information about the benthic habitat and site GPS locations were recorded. The completed photos were reviewed for content and accuracy by the ecologists and Florida Marine Research Institute (FMRI) staff and then sent to NOAA for digital compilation.
Digital Compilation of Aerial Photographs:
NGS cartographers inspected each photograph to check for completeness of delineations, photograph discrepancies, and areas of turbidity. Cartographers used a stereographic analytical plotter with NOAA's in-house software, to digitize and label the benthic communities and shoreline features seen on the aerial photographs. In many cases, the cartographers were able to provide additional detail because of the three-dimensional views permitted by the analytical plotter. The compiled data were checked by NOAA staff.
Quality Control:
A review of the data was conducted in three phases: 1) an on-line review to ensure line and attribute completeness, comparison to the ecologists' delineations, and positional accuracy; 2) a review of 1:48,000 scale maps of the compiled data against the original source photos; and 3) a review of 1:24,000 scale maps of the compiled data against the original delineated photographs for polygonal shape and attributes.