Visual and passive acoustic surveys for whales and dolphins (cetaceans, pronounced "seh-tay-shens") are commonly used to collect the data needed to assess cetacean abundance across broad areas. These ship-based surveys are conducted using line-transect methodology and include traversing predetermined tracklines at 10 knots while searching and listening for cetacean groups. During surveys like HICEAS, visual observers look for cetaceans and seabirds from the ship's flying bridge during daylight hours using "big-eye" and hand-held binoculars. Acousticians use a hydrophone array that is towed behind the ship day and night to listen for vocal groups of cetaceans and record their vocalizations. Twice per day, at sunrise and at sunset the ship stops the survey and deploys a CTD to measure the characteristics of the water column, important information for understand cetacean and seabird habitat. Often other types of sampling or collaborative research also take place aboard the ship during surveys like HICEAS. These projects could include collection of aerial imagery using a hexacopter flown over cetacean groups, launching a small boat to collect identification photos and tissue samples from individual animals, as well as deployment of satellite telemetry tags on animals to track individual movements.