Standards for Hydrographic Surveys


Hydrographic surveying is undergoing fundamental changes in measurement technology. The advent of satellite positioning systems, multibeam and multitransducer acoustic systems and sophisticated data processing systems have drastically changed the way hydrographic surveys are conducted. With these advanced technologies, the Canadian Hydrographic Service and contractors can now collect data with higher precision and quality. It is therefore necessary to update the standards taking into account these technological advancements.

The required positioning accuracy in previous versions of SSO was largely based on the practical limitations of draftsmanship at a given scale. Automated data management allows data to be presented at any scale. Therefore, the accuracy requirements for positions in this standard are a function of the errors contributed by positioning and sounding systems to some degree, but is mostly based on the perceived accuracy requirements of the user.

These standards are based on those of the IHO. The CHS adopted the conclusions of the S44 working group of this organization on the evaluation of the measurement equipment technologies stating that it is likely that many hydrographic surveys will continue to be conducted with single beam echo sounders that only sample discrete profiles of the seafloor, with the 100% seafloor search only being employed in critical areas and/or in areas where a total coverage is required. This assumption led to the decision to retain the concept of line spacing even though it is no longer directly related to survey scale.

When specifying depth accuracy, this standard departs from previous versions by specifying different accuracy requirements for different areas according to their importance for the safety of navigation. The most stringent requirements entail higher accuracy than previously specified, but for areas of less critical nature for navigation the requirements have been relaxed. Furthermore, this version makes the new requirement that surveyors strive to attribute all new data with a statistical estimate of its probable error. Equipment and procedures used to achieve the standards laid down in this document are left to the Survey Management Guideline and the quality system procedures.

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