VERTCRS["Flannan Isles height",
    VDATUM["Flannan Isles"],
    CS[vertical,1],
        AXIS["gravity-related height (H)",up,
            LENGTHUNIT["metre",1]],
    USAGE[
        SCOPE["Geodesy, engineering survey."],
        AREA["United Kingdom (UK) - Great Britain - Scotland - Flannan Isles onshore."],
        BBOX[58.21,-7.75,58.35,-7.46]],
    ID["EPSG",5748]]