The datum is defined by the observed heights of mean sea level at the 26 tide gauges and by the set of elevations of all bench marks resulting from the adjustment. A total of 106,724 kilometers of leveling was involved, constituting 246 closed circuits and 25 circuits at sea level.
George Washingtonâs Mount Vernon is located roughly 15 miles south of Washington, D.C. and 8 miles south of Alexandria, Virginia on the banks of the Potomac River, at the southern end of the George Washington Memorial Parkway.
Mount Vernon's largest and most impressive park, comprised of 480 acres, is located at the south end of the city. A 1.5 mile paved road leads to the top of Little Mountain, an elevation gain of 934 feet. There are 2 viewpoints that provide a spectacular look at the Skagit Valley, San Juan Islands, Olympic Mountains and the tulip fields.