Alaska Digitize Project

Processing methodology for the seafloor substrate data required multiple steps to georegister, digitize, clean, and validate the datasets. Sediments such as gravel, sand, and mud were available as verbal notations on the smooth sheets and the data on any one smooth sheet were digitized by one person and then proofed by another. Once the locations of the sediment point data were collected and notations were quality controlled, the sediment data were then converted to numerical values using the dbSEABED program. Essentially the program uses fuzzy set theory to assign relative weights to each word in a verbal description and then calculates a grain-size parameter using a mathematical equation of the whole description (USGS, usSEABED). In this way, a variety of word-based data may be quantified and subsequently gridded to make surfaces of the seafloor sediments. Once through the program, the sediment data were compiled in the usSEABED format with multiple attributes, where mean grain size is the primary attribute and additional quantitative and categorical data are available, such as percent gravel, sand, and mud (0-100%) and rock membership (0:1) (USGS, usSEABED).