The level of the ocean's surface, especially the level halfway between mean high and low tide, used as a standard in reckoning land elevation or sea depths.
海洋表面的水位，尤其是在平均高水位和低水位之间的平均位置的水位，用作计算陆地海拔和海水深度的标准。
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The generally accepted standard is 1020 watts per square meter at sealevel.