DATA

All data recorded during a survey include the time that the data were collected and specific information about the data-collection process. Examples of this information are survey line start/end times, time of core sampling, and beginning/ending times of camera lines. Using time of collection, the data are keyed to a master navigation log that contains the individual satellite (GPS) fixes (locations) or transponder signals (ranging) recorded at the time of the fixes. This log includes the time from the start of the survey (often departure from port) to the conclusion (return to port). Table 1 is an excerpt from the navigation log for the 1994 survey during which the bottom photographs were taken (Figure 3). The full log has a navigational fix every 10 seconds, which is a greater data density than is required for analysis of the photographs in this study. Table 1 has been desampled to include only 1-minute fixes. Figure 4 displays a small window of the survey area with time annotated along the tracklines.

Tables 2 and 3 are examples of the tabulations generated for each piece of data collected during the surveys. Table 2 records the deployment history of various pieces of equipment, that is, when pieces of equipment were turned on or off. These records cover discrete spans of time and are subsets of the complete survey time. The 1994 camera-survey segments are plotted in blue in Figure 3. Table 3 lists observations from still photographs, which were collected with a 35-mm underwater still camera loaded with 50-ft rolls of film (approximately 400 frames per roll). Shots were taken every 1.5 minute until the film was depleted (as long as 10 hours). Observations of bottom morphology and inferred current direction from each of the photographs were tabulated (Figure 5). Consecutive photographs showing the same characteristics were grouped into a single entry with the inclusive start and end times. Individual photographs showing features unlike the preceding or following ones in time sequence were entered as a single record with the same start and end time.