Gaps in sequential photo numbers exist. If the camera was triggered accidentally on deck or the photograph was of poor quality or location (e.g. photograph within water column), the photograph was not saved.
Blackwood and Parolski, 2001
Differential Global Positioning System (DGPS) navigation data were acquired with a Communications Systems International (CSI), Inc. LGBX Pro receiver. The CSI LGBX Pro received positions from a DGPS antenna located on the port, aft roof of the R/V Rafael cabin. DGPS positions were recorded within HYPACK (www.hypack.com) navigation software. Offsets between the DGPS antenna and the mini-SEABOSS were not measured. DGPS accuracy is 1 to 3 meters, depending on the distance from a US Coast Guard coastal repeater station (<http://www.navcen.uscg.gov/>). However, the horizontal position of the mini-SEABOSS during sample collection is assumed to be +/- 10 meters at best, due to a lack of precise positional data at the time of sample recovery.
With the mini-SEABOSS deployed, the research vessel was allowed to drift with occasional power from the vessel to control drift direction. Bottom photographs were acquired at user-selected locations along the drift. Video drift position was derived from the HYPACK navigation files based on start and end times. The drift navigation was merged with the digital photographs based on time of day.
Grab samples of the surficial sediment were collected at 15 stations, typically at the end of a drift. The upper 2 cm of sediment was scraped from the surface of the sample for texture analysis. Sediment samples were collected at locations with relatively fine-grained sediment (sand or mud). Samples were not collected in gravel or cobble areas where gravel prevented full closure of the sampler and resulted in a washed-out sample.
A total of 13 bottom samples were submitted for grain-size analysis. Two partially recovered, washed-out samples were not submitted. Grain-size analysis was performed at the USGS Sediment Laboratory at WHCMSC using methods described by Poppe and others (2005).
Sample locations for sample 1 and 2 were read from the video time stamp, as HYPACK navigation was not available. The position information at the end of the video drift was used as position of the sample. (Samples were acquired at the end of video drifts).
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(gis_catalog/seaboss/photos/bottomphotos155 and gis_catalog/seaboss/photos/bottomphotos156).