Preliminary hard and soft bottom seafloor substrate map derived from an unsupervised classification of gridded backscatter and bathymetry derivatives at Saipan Island, Commonwealth of the Northern Mariana Islands (CNMI).

Preliminary hard and soft seafloor substrate map derived from an unsupervised classification of multibeam backscatter and bathymety derivatives at Saipan Island, Commonwealth of the Northern Mariana Islands (CNMI). The dataset was derived using Reson 8101 backscatter data, bathymetric variance and bathymetric rugosity. The sonar frequency is 240 kHz for the Reson 8101 backscatter data, which were resampled to a 5 m grid cell size prior to the classification. Initial supervised classifications of the backscatter data into hard and soft seafloor substrates, using seafloor photographs for groundtruthing and to define regions of interest, were used to define unsupervised class types and to visually evaluate the accuracy of the unsupervised classification seafloor substrate map. However, the backscatter dataset collected at Saipan in 2003 is extremely low quality because the data were collected at high speeds, power settings were changed during acquisition, and emphasis was not placed on collecting high quality backscatter data. The Saipan survey was one of the first R/V AHI surveys. The backscatter data used in this analysis are the third iteration of processed data and extreme caution should be used when examining these data to locate habitat of biological significance. The map should be used in conjunction with bathymetric derivatives such as rugossity, slope, and Bathymetric Position Index (BPI).