Soundings - from the old French sonder, meaning to measure the depth. Soundings are what the marine surveyors of the Coast and Geodetic Survey obtained, day in and day out, all day long as small ships and survey boats steered their lines to the rhythm of "On the next! Stand-byyyy! Mark It!'
The members of the survey team would read the depth, measure the angles to determine the position of the boat, and plot that position with a three-arm protractor on the boat sheet and print the depth to boot. Then the cycle would start again. Millions of soundings were obtained this way to make the charts that led mariners safely to our shores for the first century and a half of the Coast Survey's existence. Then came the age of electronics.