EPSG:9451 - BI height

{
  "$schema": "https://proj.org/schemas/v0.7/projjson.schema.json",
  "type": "VerticalCRS",
  "name": "BI height",
  "datum_ensemble": {
    "name": "British Isles height ensemble",
    "members": [
      {
        "name": "Malin Head",
        "id": {
          "authority": "EPSG",
          "code": 5130
        }
      },
      {
        "name": "Belfast Lough",
        "id": {
          "authority": "EPSG",
          "code": 5131
        }
      },
      {
        "name": "Ordnance Datum Newlyn",
        "id": {
          "authority": "EPSG",
          "code": 5101
        }
      },
      {
        "name": "Ordnance Datum Newlyn (Offshore)",
        "id": {
          "authority": "EPSG",
          "code": 1164
        }
      },
      {
        "name": "Ordnance Datum Newlyn (Orkney Isles)",
        "id": {
          "authority": "EPSG",
          "code": 5138
        }
      },
      {
        "name": "Lerwick",
        "id": {
          "authority": "EPSG",
          "code": 5140
        }
      },
      {
        "name": "Stornoway",
        "id": {
          "authority": "EPSG",
          "code": 5144
        }
      },
      {
        "name": "Douglas",
        "id": {
          "authority": "EPSG",
          "code": 5148
        }
      },
      {
        "name": "St. Marys",
        "id": {
          "authority": "EPSG",
          "code": 5147
        }
      }
    ],
    "accuracy": "0.4",
    "id": {
      "authority": "EPSG",
      "code": 1288
    }
  },
  "coordinate_system": {
    "subtype": "vertical",
    "axis": [
      {
        "name": "Gravity-related height",
        "abbreviation": "H",
        "direction": "up",
        "unit": "metre"
      }
    ]
  },
  "scope": "Spatial referencing.",
  "area": "United Kingdom (UK) - offshore to boundary of UKCS within 49°45'N to 61°N and 9°W to 2°E; onshore Great Britain (England, Wales and Scotland) and Northern Ireland. Ireland onshore. Isle of Man onshore.",
  "bbox": {
    "south_latitude": 49.75,
    "west_longitude": -10.85,
    "north_latitude": 61.01,
    "east_longitude": 2.01
  },
  "id": {
    "authority": "EPSG",
    "code": 9451
  }
}

{'crs_wkt': 'VERTCRS["BI height",ENSEMBLE["British Isles height '
            'ensemble",MEMBER["Malin Head"],MEMBER["Belfast '
            'Lough"],MEMBER["Ordnance Datum Newlyn"],MEMBER["Ordnance Datum '
            'Newlyn (Offshore)"],MEMBER["Ordnance Datum Newlyn (Orkney '
            'Isles)"],MEMBER["Lerwick"],MEMBER["Stornoway"],MEMBER["Douglas"],MEMBER["St. '
            'Marys"],ENSEMBLEACCURACY[0.4]],CS[vertical,1],AXIS["gravity-related '
            'height (H)",up,LENGTHUNIT["metre",1]],USAGE[SCOPE["Spatial '
            'referencing."],AREA["United Kingdom (UK) - offshore to boundary '
            "of UKCS within 49°45'N to 61°N and 9°W to 2°E; onshore Great "
            'Britain (England, Wales and Scotland) and Northern Ireland. '
            'Ireland onshore. Isle of Man '
            'onshore."],BBOX[49.75,-10.85,61.01,2.01]],ID["EPSG",9451]]'}