EPSG:7874

COORDINATEOPERATION["EGM2008 height to POM08 height (1)",
    VERSION["QC-Png Gulf-Cen"],
    SOURCECRS[
        VERTCRS["EGM2008 height",
            VDATUM["EGM2008 geoid"],
            CS[vertical,1],
                AXIS["gravity-related height (H)",up,
                    LENGTHUNIT["metre",1]],
            ID["EPSG",3855]]],
    TARGETCRS[
        VERTCRS["POM08 height",
            VDATUM["Port Moresby 2008"],
            CS[vertical,1],
                AXIS["gravity-related height (H)",up,
                    LENGTHUNIT["metre",1]],
            ID["EPSG",7841]]],
    METHOD["Vertical Offset",
        ID["EPSG",9616]],
    PARAMETER["Vertical Offset",-0.93,
        LENGTHUNIT["metre",1],
        ID["EPSG",8603]],
    OPERATIONACCURACY[0.0],
    USAGE[
        SCOPE["Derivation of gravity-related heights from GNSS observations."],
        AREA["Papua New Guinea - onshore - Gulf province east of 144°24'E, Central province and National Capital District."],
        BBOX[-10.42,144.4,-6.67,149.67]],
    ID["EPSG",7874],
    REMARK["Defines POM08 heights."]]

proj4.defs("EPSG:7874","+proj=geogoffset +dh=-0.93");

{
    "$schema": "https://proj.org/schemas/v0.7/projjson.schema.json",
    "type": "Transformation",
    "name": "EGM2008 height to POM08 height (1)",
    "source_crs": {
        "type": "VerticalCRS",
        "name": "EGM2008 height",
        "datum": {
            "type": "VerticalReferenceFrame",
            "name": "EGM2008 geoid"
        },
        "coordinate_system": {
            "subtype": "vertical",
            "axis": [
                {
                    "name": "Gravity-related height",
                    "abbreviation": "H",
                    "direction": "up",
                    "unit": "metre"
                }
            ]
        },
        "id": {
            "authority": "EPSG",
            "code": 3855
        }
    },
    "target_crs": {
        "type": "VerticalCRS",
        "name": "POM08 height",
        "datum": {
            "type": "VerticalReferenceFrame",
            "name": "Port Moresby 2008"
        },
        "coordinate_system": {
            "subtype": "vertical",
            "axis": [
                {
                    "name": "Gravity-related height",
                    "abbreviation": "H",
                    "direction": "up",
                    "unit": "metre"
                }
            ]
        },
        "id": {
            "authority": "EPSG",
            "code": 7841
        }
    },
    "method": {
        "name": "Vertical Offset",
        "id": {
            "authority": "EPSG",
            "code": 9616
        }
    },
    "parameters": [
        {
            "name": "Vertical Offset",
            "value": -0.93,
            "unit": "metre",
            "id": {
                "authority": "EPSG",
                "code": 8603
            }
        }
    ],
    "accuracy": "0.0",
    "scope": "Derivation of gravity-related heights from GNSS observations.",
    "area": "Papua New Guinea - onshore - Gulf province east of 144°24'E, Central province and National Capital District.",
    "bbox": {
        "south_latitude": -10.42,
        "west_longitude": 144.4,
        "north_latitude": -6.67,
        "east_longitude": 149.67
    },
    "id": {
        "authority": "EPSG",
        "code": 7874
    },
    "remarks": "Defines POM08 heights."
}

<?xml version="1.0" encoding="utf-8"?>
<Map srs="+proj=geogoffset +dh=-0.93">
	<Layer srs="+proj=geogoffset +dh=-0.93">
	</Layer>
</Map>

INSERT into spatial_ref_sys (srid, auth_name, auth_srid, proj4text, srtext) values ( 7874, 'EPSG', 7874, '+proj=geogoffset +dh=-0.93', 'None');