EPSG:9318

COORDINATEOPERATION["NZVD2016 height to Moturiki 1953 height (2)",
    VERSION["LINZ-NZ MOTU gtx"],
    SOURCECRS[
        VERTCRS["NZVD2016 height",
            VDATUM["New Zealand Vertical Datum 2016"],
            CS[vertical,1],
                AXIS["gravity-related height (H)",up,
                    LENGTHUNIT["metre",1]],
            ID["EPSG",7839]]],
    TARGETCRS[
        VERTCRS["Moturiki 1953 height",
            VDATUM["Moturiki 1953"],
            CS[vertical,1],
                AXIS["gravity-related height (H)",up,
                    LENGTHUNIT["metre",1]],
            ID["EPSG",5764]]],
    METHOD["Vertical Offset by Grid Interpolation (gtx)",
        ID["EPSG",1084]],
    PARAMETERFILE["Vertical offset file","motuht1953-nzvd2016.gtx"],
    INTERPOLATIONCRS[
        GEOGCRS["NZGD2000",
            DATUM["New Zealand Geodetic Datum 2000",
                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]]]],
    OPERATIONACCURACY[0.02],
    USAGE[
        SCOPE["Change of height to a different vertical reference surface."],
        AREA["New Zealand - North Island - Moturiki vertical CRS area."],
        BBOX[-40.59,174.57,-37.52,177.26]],
    ID["EPSG",9318],
    REMARK["Derived at 519 control points. Mean offset 0.309m, standard deviation 0.071m, maximum difference from mean 0.231m. Supersedes NZVD2016 height to Moturiki 1953 height (1) (code 7866) after change of grid file format."]]

proj4.defs("EPSG:9318","+proj=vgridshift +grids=nz_linz_motuht1953-nzvd2016.tif +multiplier=1");

{
    "$schema": "https://proj.org/schemas/v0.7/projjson.schema.json",
    "type": "Transformation",
    "name": "NZVD2016 height to Moturiki 1953 height (2)",
    "source_crs": {
        "type": "VerticalCRS",
        "name": "NZVD2016 height",
        "datum": {
            "type": "VerticalReferenceFrame",
            "name": "New Zealand Vertical Datum 2016"
        },
        "coordinate_system": {
            "subtype": "vertical",
            "axis": [
                {
                    "name": "Gravity-related height",
                    "abbreviation": "H",
                    "direction": "up",
                    "unit": "metre"
                }
            ]
        },
        "id": {
            "authority": "EPSG",
            "code": 7839
        }
    },
    "target_crs": {
        "type": "VerticalCRS",
        "name": "Moturiki 1953 height",
        "datum": {
            "type": "VerticalReferenceFrame",
            "name": "Moturiki 1953"
        },
        "coordinate_system": {
            "subtype": "vertical",
            "axis": [
                {
                    "name": "Gravity-related height",
                    "abbreviation": "H",
                    "direction": "up",
                    "unit": "metre"
                }
            ]
        },
        "id": {
            "authority": "EPSG",
            "code": 5764
        }
    },
    "interpolation_crs": {
        "type": "GeographicCRS",
        "name": "NZGD2000",
        "datum": {
            "type": "GeodeticReferenceFrame",
            "name": "New Zealand Geodetic Datum 2000",
            "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"
                }
            ]
        },
        "id": {
            "authority": "EPSG",
            "code": 4167
        }
    },
    "method": {
        "name": "Vertical Offset by Grid Interpolation (gtx)",
        "id": {
            "authority": "EPSG",
            "code": 1084
        }
    },
    "parameters": [
        {
            "name": "Vertical offset file",
            "value": "motuht1953-nzvd2016.gtx",
            "id": {
                "authority": "EPSG",
                "code": 8732
            }
        }
    ],
    "accuracy": "0.02",
    "scope": "Change of height to a different vertical reference surface.",
    "area": "New Zealand - North Island - Moturiki vertical CRS area.",
    "bbox": {
        "south_latitude": -40.59,
        "west_longitude": 174.57,
        "north_latitude": -37.52,
        "east_longitude": 177.26
    },
    "id": {
        "authority": "EPSG",
        "code": 9318
    },
    "remarks": "Derived at 519 control points. Mean offset 0.309m, standard deviation 0.071m, maximum difference from mean 0.231m. Supersedes NZVD2016 height to Moturiki 1953 height (1) (code 7866) after change of grid file format."
}

<?xml version="1.0" encoding="utf-8"?>
<Map srs="+proj=vgridshift +grids=nz_linz_motuht1953-nzvd2016.tif +multiplier=1">
	<Layer srs="+proj=vgridshift +grids=nz_linz_motuht1953-nzvd2016.tif +multiplier=1">
	</Layer>
</Map>

INSERT into spatial_ref_sys (srid, auth_name, auth_srid, proj4text, srtext) values ( 9318, 'EPSG', 9318, '+proj=vgridshift +grids=nz_linz_motuht1953-nzvd2016.tif +multiplier=1', 'None');