95 kHz backscatter data are routinely collected by the Canadian Hydrographic Service using shallow water multibeam sonars (Simrad EM100 and EM1000 systems). This data is co-registered with high resolution bathymetry and provides a means of generating sidescan images of the seabed which can be correlated with the bottom topography. Changes in amplifier gains are corrected so that the authors can compare the acoustic signature of distinct seabed lithologies for use as part of a remote sediment classification scheme. In order to groundtruth the acoustic signatures, an experiment is underway in the Bay of Fundy (using the intertidal zone where tidal ranges locally exceed 15 m) using terrestrial survey and sampling methods. As part of the experiment, interactive graphical tools have been developed that allow the data to be processed as it is acquired and enable near-real time data quality assessment.< >
Since the advent of Global Navigation Satellite Systems, it has been possible to perform hydrographic survey reductions through the ellipsoid, which has the potential to simplify operations and improve bathymetric products. This technique requires a spatially continuous separation surface connecting chart datum (CD) to a geodetic ellipsoid. The Canadian Hydrographic Service (CHS), with support from the Canadian Geodetic Survey, has developed a new suite of such surfaces, termed Hydrographic Vertical Separations Surfaces, or HyVSEPs, for CD and seven tidal levels. They capture the spatial variability of the tidal datum and levels between tide gauges and offshore using semiempirical models coupling observations at tide stations with relative sea-level rise estimates, dynamic ocean model solutions, satellite altimetry, and a geoid model. HyVSEPs are available for all tidal waters of Canada, covering over seven million square kilometers of ocean and more than 200,000 kilometers of shoreline. This document provides an overview of the CHS's modeling approach, tools, methods, and procedures.
Over the past 50 years, the hydrographic community has progressed from the humble leadline for single spot depths to sophisticated multibeam sounding systems capable of charting the entire seafloor. Canada now extensively uses this technology in its surveying operations. There are many benefits to using the latest swath systems, especially in the coastal margins and inland waters where, for instance, channel monitoring and dredging raise safety, economic and environmental issues. Utilizing multibeam systems reduces survey time, extends bottom coverage and contributes to conserving survey resources. Multibeam systems are expensive and the complexity of the system often requires high maintenance. In addition the software used for acquiring, processing and displaying the collected information is still maturing. Data cleaning algorithms to accommodate data collection rates that at times exceed 3000 data points per second are required. Canada has been dealing with those aspects of swath sounding for a decade now. Continuous research and development in the subject gave berth to new technologies and new acquisition and processing techniques. This paper summarizes the Canadian experiences in swath sounding and discusses its future developments and direction within the Canadian Hydrographic Service.
