Continuous Vertical Datum Separations for Canadian Waters

Since 1883, the Canadian Hydrographic Service (CHS) has studied the oceans to ensure safe navigation of Canada's waterways. Bathymetric surveys, and the nautical charts and products they produce, play an important role in maritime transportation, ocean and freshwater mapping, identifying coastal hazards, and sovereignty -- the four pillars of the CHS mandate. Over the past 130 years, hydrography has evolved from single-point measurements with weighted lines to the use of multibeam echosounders. To accomplish this "through the ellipsoid" reduction process, the separation between chart datum (CD), the reference for all charted depths and the reference ellipsoid must be known. This article will present an overview of the CVDCW project and its products, Hydrographic Vertical Separation Surfaces (HyVSEPs). The CVDCW has developed HyVSEPs for a range of tidal target water levels. All are valuable resources for hydrography, coastal engineering, coastal planning, ecosystem management, or any effort requiring knowledge of vertical or horizontal water level target or datum positioning.