EPSG:9541

COMPD_CS["RGSPM06 + Danger 1950 height",
    GEOGCS["RGSPM06",
        DATUM["Reseau_Geodesique_de_Saint_Pierre_et_Miquelon_2006",
            SPHEROID["GRS 1980",6378137,298.257222101,
                AUTHORITY["EPSG","7019"]],
            AUTHORITY["EPSG","1038"]],
        PRIMEM["Greenwich",0,
            AUTHORITY["EPSG","8901"]],
        UNIT["degree",0.0174532925199433,
            AUTHORITY["EPSG","9122"]],
        AUTHORITY["EPSG","4463"]],
    VERT_CS["Danger 1950 height",
        VERT_DATUM["Danger 1950",2005,
            AUTHORITY["EPSG","5190"]],
        UNIT["metre",1,
            AUTHORITY["EPSG","9001"]],
        AXIS["Gravity-related height",UP],
        AUTHORITY["EPSG","5792"]],
    AUTHORITY["EPSG","9541"]]

COMPOUNDCRS["RGSPM06 + Danger 1950 height",
    GEOGCRS["RGSPM06",
        DATUM["Reseau Geodesique de Saint Pierre et Miquelon 2006",
            ELLIPSOID["GRS 1980",6378137,298.257222101,
                LENGTHUNIT["metre",1]]],
        PRIMEM["Greenwich",0,
            ANGLEUNIT["degree",0.0174532925199433]],
        CS[ellipsoidal,2],
            AXIS["geodetic latitude (Lat)",north,
                ORDER[1],
                ANGLEUNIT["degree",0.0174532925199433]],
            AXIS["geodetic longitude (Lon)",east,
                ORDER[2],
                ANGLEUNIT["degree",0.0174532925199433]]],
    VERTCRS["Danger 1950 height",
        VDATUM["Danger 1950"],
        CS[vertical,1],
            AXIS["gravity-related height (H)",up,
                LENGTHUNIT["metre",1]]],
    USAGE[
        SCOPE["Spatial referencing."],
        AREA["St Pierre and Miquelon - onshore."],
        BBOX[46.69,-56.48,47.19,-56.07]],
    ID["EPSG",9541]]

GEOGCS["GCS_RGSPM_2006",
    DATUM["D_Reseau_Geodesique_de_St_Pierre_et_Miquelon_2006",
        SPHEROID["GRS_1980",6378137.0,298.257222101]],
    PRIMEM["Greenwich",0.0],
    UNIT["Degree",0.0174532925199433]],
VERTCS["Danger_1950",
    VDATUM["Danger_1950"],
    PARAMETER["Vertical_Shift",0.0],
    PARAMETER["Direction",1.0],
    UNIT["Meter",1.0]]

proj4.defs("EPSG:9541","+proj=longlat +ellps=GRS80 +vunits=m +no_defs +type=crs");

{
    "$schema": "https://proj.org/schemas/v0.7/projjson.schema.json",
    "type": "CompoundCRS",
    "name": "RGSPM06 + Danger 1950 height",
    "components": [
        {
            "type": "GeographicCRS",
            "name": "RGSPM06",
            "datum": {
                "type": "GeodeticReferenceFrame",
                "name": "Reseau Geodesique de Saint Pierre et Miquelon 2006",
                "ellipsoid": {
                    "name": "GRS 1980",
                    "semi_major_axis": 6378137,
                    "inverse_flattening": 298.257222101
                }
            },
            "coordinate_system": {
                "subtype": "ellipsoidal",
                "axis": [
                    {
                        "name": "Geodetic latitude",
                        "abbreviation": "Lat",
                        "direction": "north",
                        "unit": "degree"
                    },
                    {
                        "name": "Geodetic longitude",
                        "abbreviation": "Lon",
                        "direction": "east",
                        "unit": "degree"
                    }
                ]
            }
        },
        {
            "type": "VerticalCRS",
            "name": "Danger 1950 height",
            "datum": {
                "type": "VerticalReferenceFrame",
                "name": "Danger 1950"
            },
            "coordinate_system": {
                "subtype": "vertical",
                "axis": [
                    {
                        "name": "Gravity-related height",
                        "abbreviation": "H",
                        "direction": "up",
                        "unit": "metre"
                    }
                ]
            }
        }
    ],
    "scope": "Spatial referencing.",
    "area": "St Pierre and Miquelon - onshore.",
    "bbox": {
        "south_latitude": 46.69,
        "west_longitude": -56.48,
        "north_latitude": 47.19,
        "east_longitude": -56.07
    },
    "id": {
        "authority": "EPSG",
        "code": 9541
    }
}

<?xml version="1.0" encoding="utf-8"?>
<Map srs="+proj=longlat +ellps=GRS80 +vunits=m +no_defs +type=crs">
	<Layer srs="+proj=longlat +ellps=GRS80 +vunits=m +no_defs +type=crs">
	</Layer>
</Map>

INSERT into spatial_ref_sys (srid, auth_name, auth_srid, proj4text, srtext) values ( 9541, 'EPSG', 9541, '+proj=longlat +ellps=GRS80 +vunits=m +no_defs +type=crs', 'COMPD_CS["RGSPM06 + Danger 1950 height",GEOGCS["RGSPM06",DATUM["Reseau_Geodesique_de_Saint_Pierre_et_Miquelon_2006",SPHEROID["GRS 1980",6378137,298.257222101,AUTHORITY["EPSG","7019"]],AUTHORITY["EPSG","1038"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4463"]],VERT_CS["Danger 1950 height",VERT_DATUM["Danger 1950",2005,AUTHORITY["EPSG","5190"]],UNIT["metre",1,AUTHORITY["EPSG","9001"]],AXIS["Gravity-related height",UP],AUTHORITY["EPSG","5792"]],AUTHORITY["EPSG","9541"]]');