Small-Boat Surveys in Shallow Water
| Book title | Marine Habitat Mapping Technology for Alaska |
|---|---|
| Year | 2008 |
| Article DOI | 10.4027/mhmta.2008.05 (about DOIs) |
| Pages | 71–89 |
| PDF link* | View full text in PDF format [1 MB] |
*This low-resolution PDF is optimized for viewing on screen. High-resolution chapters are available on CD only.
Abstract
The Canadian Hydrographic Service has for many years used small boats (launches) to conduct surveys in shallow water for the purposes 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 point. For about the next half-century, soundings were acquired by single-beam echo sounder which evolved from wide-beam analogue equipment to modern digital narrow-beam sounders with capacity for classification of the returning acoustic pulse (not discussed in this paper). Seabed samples (for charting purposes) were acquired in a separate operation involving either an armed leadline or grab samplers deployed using a winch.
In the last decade, most shallow-water surveys have been conducted using multibeam echo sounder systems (MBES): for practical reasons we limit the operational depths to about 10 meters. Bathymetric (phase-measuring) side scan sonars may allow us to look from this operational depth limit into the shoreline. For the moment, however, the way we collect bathymetry using these modern tools is leaving a gap between the low-water line and the adjacent survey data. More and more, the data acquired are being used less for navigational safety and more for myriad other applications.
This paper will look at some of the operational issues of acquiring high-resolution bathymetry and acoustic backscatter information in shallow water aboard hydrographic launches.
