## Materials and Methods
### In Situ Data  
In order to train the classification algorithm, a variety of in situ field reference data were used within selected test areas. The primary information came from a database of 1653 GPS-referenced underwater video surveys collected in the Dominican Republic and Saint Croix, UVVI (Figure 6) between 2017-2019, corresponding to the date range of the PS image composite. Each of these field transects was collected as part of a local scale mapping project in collaboration with the Global Airborne Observatory (GAO) and designed to assess a diverse array of benthic compositions. Transect locations were selected based on a strategic image interpretation sample of each benthic class and a SeaViewer Sea-Drop 6000 HD (Tampa, FL, USA) underwater video camera with 30 m vertical cable was used to collect the video. Corresponding bathymetric field measurements were simultaneously collected using a Lowrance Elite7 Ti (Tulsa, OK, USA) system with a xSonic P319 (50/200 kHz) transducer and 10 Hz GPS receiver that collected continuous depth readings at 3 pts/s along each transect. These measurements were previously used to develop a new adaptive bathymetry estimation algorithm for PS imagery and adaptively tunes a depth  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Structure** & \multicolumn{2}{c}{**Benthic Cover**} \\ \hline
**Type** & **Level 1** & **Level 2** \\ \hline Hardbottom Reef & Reef & Coral/Algae (Fringing and Patch) \\ \hline  & & Reef Crest \\ \hline  & & Reef Back (Inner flat) \\ \hline  & & Reef Fore (Outer flat) \\ \hline  & & Spur and Groove \\ \hline  & & Boulders and Rocks \\ \hline Hardbottom (Non-reef) & Hardbottom & Hardbottom with Dense Algae \\ \hline  & & Hardbottom with Sparse Algae \\ \hline Unconsolidated sediment & Seagrass & Dense Seagrass \\ \hline  & & Sparse Seagrass \\ \hline  & Sand & Sand \\ \hline  & Muddy bottom & Muddy Bottom/Estuarine \\ \hline  & & Dredged \\ \hline \hline \end{tabular}
\end{table}
Table 2: Final thirteen-class benthic habitat classification scheme selected for use in the Caribbean-wide mapping. Classifications and accuracy assessments were performed on both Level 1 and 2.  
estimator according to water column attenuation conditions with reported accuracies of RMSE = 1.22\(-\)1.86 m [36]. For each field transect, the benthic habitat type was interpreted from the videos and matched to the habitat class used in the regional classification scheme (boulders and rocks, coral/algae, hardbottom with dense algae, hardbottom with sparse algae, muddy bottom, sand, dense seagrass, sparse seagrass, and spur and groove). These survey point data were also used to train and validate respective development steps within the classification method. For example, when developing the classification approach for the different reef types, half of the georeferenced survey points were used in the classification, while the other half were used for post-classification validation. In addition to the video transects, supplemental field data, including high resolution drone data, snorkel surveys, and local knowledge were used to refine the classification results within the test areas of the Dominican Republic and Saint Croix, USVI.