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Brisbane, Australia | All this depends on the local topography as a water surface relates directly to gravity at that location and the model that the GPS family has for the GEOID is a very loose "best guess" of what that gravity model really is across the surface of the earth. In areas where there are hills etc you may find differences between the actual gravity model and the GPS model - hence the reason why there are so many localized mapping models used in the surveying industry. I've seen a 6 inch variation between the two models over 2 miles in one of the mining areas here. In the flat plains there is not much difference at all, if any. | |
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Earth's curvature
