EPSG:7406

COMPD_CS["NAD27 + NGVD29 height (ftUS)",
    GEOGCS["NAD27",
        DATUM["North_American_Datum_1927",
            SPHEROID["Clarke 1866",6378206.4,294.978698213898,
                AUTHORITY["EPSG","7008"]],
            AUTHORITY["EPSG","6267"]],
        PRIMEM["Greenwich",0,
            AUTHORITY["EPSG","8901"]],
        UNIT["degree",0.0174532925199433,
            AUTHORITY["EPSG","9122"]],
        AUTHORITY["EPSG","4267"]],
    VERT_CS["NGVD29 height (ftUS)",
        VERT_DATUM["National Geodetic Vertical Datum 1929",2005,
            AUTHORITY["EPSG","5102"]],
        UNIT["US survey foot",0.304800609601219,
            AUTHORITY["EPSG","9003"]],
        AXIS["Gravity-related height",UP],
        AUTHORITY["EPSG","5702"]],
    AUTHORITY["EPSG","7406"]]

COMPOUNDCRS["NAD27 + NGVD29 height (ftUS)",
    GEOGCRS["NAD27",
        DATUM["North American Datum 1927",
            ELLIPSOID["Clarke 1866",6378206.4,294.978698213898,
                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["NGVD29 height (ftUS)",
        VDATUM["National Geodetic Vertical Datum 1929"],
        CS[vertical,1],
            AXIS["gravity-related height (H)",up,
                LENGTHUNIT["US survey foot",0.304800609601219]]],
    USAGE[
        SCOPE["Engineering survey, topographic mapping."],
        AREA["United States (USA) - conterminous (contiguous) lower 48 states (CONUS) - onshore."],
        BBOX[24.41,-124.79,49.38,-66.91]],
    ID["EPSG",7406]]

GEOGCS["GCS_North_American_1927",
    DATUM["D_North_American_1927",
        SPHEROID["Clarke_1866",6378206.4,294.978698213898]],
    PRIMEM["Greenwich",0.0],
    UNIT["Degree",0.0174532925199433]],
VERTCS["NGVD_1929",
    VDATUM["National_Geodetic_Vertical_Datum_1929"],
    PARAMETER["Vertical_Shift",0.0],
    PARAMETER["Direction",1.0],
    UNIT["US survey foot",0.304800609601219]]

proj4.defs("EPSG:7406","+proj=longlat +datum=NAD27 +vunits=us-ft +no_defs +type=crs");

{
    "$schema": "https://proj.org/schemas/v0.7/projjson.schema.json",
    "type": "CompoundCRS",
    "name": "NAD27 + NGVD29 height (ftUS)",
    "components": [
        {
            "type": "GeographicCRS",
            "name": "NAD27",
            "datum": {
                "type": "GeodeticReferenceFrame",
                "name": "North American Datum 1927",
                "ellipsoid": {
                    "name": "Clarke 1866",
                    "semi_major_axis": 6378206.4,
                    "semi_minor_axis": 6356583.8
                }
            },
            "coordinate_system": {
                "subtype": "ellipsoidal",
                "axis": [
                    {
                        "name": "Geodetic latitude",
                        "abbreviation": "Lat",
                        "direction": "north",
                        "unit": "degree"
                    },
                    {
                        "name": "Geodetic longitude",
                        "abbreviation": "Lon",
                        "direction": "east",
                        "unit": "degree"
                    }
                ]
            },
            "remarks": "Note: this CRS includes longitudes which are POSITIVE EAST. Replaced by NAD27(76) (code 4608) in Ontario, CGQ77 (code 4609) in Quebec, Mexican Datum of 1993 (code 4483) in Mexico, NAD83 (code 4269) in Canada (excl. Ontario & Quebec) & USA."
        },
        {
            "type": "VerticalCRS",
            "name": "NGVD29 height (ftUS)",
            "datum": {
                "type": "VerticalReferenceFrame",
                "name": "National Geodetic Vertical Datum 1929"
            },
            "coordinate_system": {
                "subtype": "vertical",
                "axis": [
                    {
                        "name": "Gravity-related height",
                        "abbreviation": "H",
                        "direction": "up",
                        "unit": {
                            "type": "LinearUnit",
                            "name": "US survey foot",
                            "conversion_factor": 0.304800609601219
                        }
                    }
                ]
            }
        }
    ],
    "scope": "Engineering survey, topographic mapping.",
    "area": "United States (USA) - conterminous (contiguous) lower 48 states (CONUS) - onshore.",
    "bbox": {
        "south_latitude": 24.41,
        "west_longitude": -124.79,
        "north_latitude": 49.38,
        "east_longitude": -66.91
    },
    "id": {
        "authority": "EPSG",
        "code": 7406
    }
}

<?xml version="1.0" encoding="utf-8"?>
<Map srs="+proj=longlat +datum=NAD27 +vunits=us-ft +no_defs +type=crs">
	<Layer srs="+proj=longlat +datum=NAD27 +vunits=us-ft +no_defs +type=crs">
	</Layer>
</Map>

INSERT into spatial_ref_sys (srid, auth_name, auth_srid, proj4text, srtext) values ( 7406, 'EPSG', 7406, '+proj=longlat +datum=NAD27 +vunits=us-ft +no_defs +type=crs', 'COMPD_CS["NAD27 + NGVD29 height (ftUS)",GEOGCS["NAD27",DATUM["North_American_Datum_1927",SPHEROID["Clarke 1866",6378206.4,294.978698213898,AUTHORITY["EPSG","7008"]],AUTHORITY["EPSG","6267"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4267"]],VERT_CS["NGVD29 height (ftUS)",VERT_DATUM["National Geodetic Vertical Datum 1929",2005,AUTHORITY["EPSG","5102"]],UNIT["US survey foot",0.304800609601219,AUTHORITY["EPSG","9003"]],AXIS["Gravity-related height",UP],AUTHORITY["EPSG","5702"]],AUTHORITY["EPSG","7406"]]');