"chart datum" meaning in English

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  "lang_code": "en",
  "pos": "noun",
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      "glosses": [
        "the level below which depths are indicated and above which heights of the tides are expressed; usually mean level of low water at a spring tide"
      ],
      "id": "en-chart_datum-en-noun-r5avMlEP",
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          "nautical",
          "nautical"
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        [
          "level",
          "level"
        ],
        [
          "depth",
          "depth"
        ],
        [
          "height",
          "height"
        ],
        [
          "tide",
          "tide"
        ],
        [
          "spring tide",
          "spring tide"
        ]
      ],
      "raw_glosses": [
        "(nautical) the level below which depths are indicated and above which heights of the tides are expressed; usually mean level of low water at a spring tide"
      ],
      "topics": [
        "nautical",
        "transport"
      ]
    }
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  "word": "chart datum"
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  "lang_code": "en",
  "pos": "noun",
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      "glosses": [
        "the level below which depths are indicated and above which heights of the tides are expressed; usually mean level of low water at a spring tide"
      ],
      "links": [
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          "nautical",
          "nautical"
        ],
        [
          "level",
          "level"
        ],
        [
          "depth",
          "depth"
        ],
        [
          "height",
          "height"
        ],
        [
          "tide",
          "tide"
        ],
        [
          "spring tide",
          "spring tide"
        ]
      ],
      "raw_glosses": [
        "(nautical) the level below which depths are indicated and above which heights of the tides are expressed; usually mean level of low water at a spring tide"
      ],
      "topics": [
        "nautical",
        "transport"
      ]
    }
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  "word": "chart datum"
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