Contribution of Tide Gauges for the Determination of W₀ in Canada

Canada plans to implement a geoid-based and GNSS-accessible vertical datum in 2013 in order to replace the existing Canadian Geodetic Vertical Datum of 1928, which no longer meets the needs of the modern user in terms of accuracy and accessibility. One of the primary concerns when realizing a geoid-based vertical datum is to determine the W ₀ value that will represent the potential of the zero-height surface. Thus, the objective of this study is to determine W ₀ by averaging the potential of points on the mean water surface by using Canadian tide gauge records and GOCE-based global geopotential models. The GOCE-based models are extended with the high-resolution gravity field model EGM2008 in order to assess the effect of the omission error on the computation of W ₀. Similarly, the regional gravimetric geoid model CGG2010 is also used for the estimation of W ₀ in order to assess the effect of higher frequency contributions of the gravity field, which are missing from the GOCE-based global geopotential models. Additionally, sea surface topography models are utilized in order to validate the W ₀ results based on tide gauges and to estimate W ₀ values for North America. The W ₀ values obtained using Canadian tide gauges and high resolution gravity field and geoid models are not statistically different from the International Earth Rotation and Reference Systems Service 2010 global conventional value of 62,636,856.00 m²/s².