VERTCRS["MHWS height",
    VDATUM["Mean High Water Spring Tides"],
    CS[vertical,1],
        AXIS["gravity-related height (H)",up,
            LENGTHUNIT["metre",1]],
    USAGE[
        SCOPE["Hydrography and nautical charting."],
        AREA["World."],
        BBOX[-90,-180,90,180]],
    ID["EPSG",5870]]