Small-Boat Surveys in Shallow Water

Abstract

The Canadian Hydrographic Service (CHS) has for many years used small boats (launches) to conduct surveys in shallow water for the purpose of nautical charting. Prior to WW II, soundings would have been taken by leadline, providing depths and often some limited information about the seafloor type at each sample. For about the next half-century, soundings were acquired by single-beam echosounder, which evolved from wide-beam analogue equipment to modern digital narrow-beam sounders with capacity for clas sification of the returning acoustic pulse. Seabed samples (for charting purposes) were acquired in a separate operation involving either an armed leadline or grab samplers deployed using a winch. Sidescan sonars evolved from an oblique-looking single-beam transducer to modern high-resolution systems of today. In the last decade, most shallow-water surveys have been