EPSG:9315

COORDINATEOPERATION["NZVD2016 height to Dunedin-Bluff 1960 height (2)",
    VERSION["LINZ-NZ DUBL 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["Dunedin-Bluff 1960 height",
            VDATUM["Dunedin-Bluff 1960"],
            CS[vertical,1],
                AXIS["gravity-related height (H)",up,
                    LENGTHUNIT["metre",1]],
            ID["EPSG",4458]]],
    METHOD["Vertical Offset by Grid Interpolation (gtx)",
        ID["EPSG",1084]],
    PARAMETERFILE["Vertical offset file","dublht1960-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 - South Island - Dunedin-Bluff vertical CRS area."],
        BBOX[-46.73,166.37,-44.52,169.95]],
    ID["EPSG",9315],
    REMARK["Derived at 205 control points. Mean offset 0.254m, standard deviation 0.039m, maximum difference from mean 0.11m. Supersedes NZVD2016 height to Dunedin-Bluff 1960 height (1) (code 7863) after change of grid file format."]]

proj4.defs("EPSG:9315","+proj=vgridshift +grids=nz_linz_dublht1960-nzvd2016.tif +multiplier=1");

{
    "$schema": "https://proj.org/schemas/v0.7/projjson.schema.json",
    "type": "Transformation",
    "name": "NZVD2016 height to Dunedin-Bluff 1960 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": "Dunedin-Bluff 1960 height",
        "datum": {
            "type": "VerticalReferenceFrame",
            "name": "Dunedin-Bluff 1960"
        },
        "coordinate_system": {
            "subtype": "vertical",
            "axis": [
                {
                    "name": "Gravity-related height",
                    "abbreviation": "H",
                    "direction": "up",
                    "unit": "metre"
                }
            ]
        },
        "id": {
            "authority": "EPSG",
            "code": 4458
        }
    },
    "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": "dublht1960-nzvd2016.gtx",
            "id": {
                "authority": "EPSG",
                "code": 8732
            }
        }
    ],
    "accuracy": "0.02",
    "scope": "Change of height to a different vertical reference surface.",
    "area": "New Zealand - South Island - Dunedin-Bluff vertical CRS area.",
    "bbox": {
        "south_latitude": -46.73,
        "west_longitude": 166.37,
        "north_latitude": -44.52,
        "east_longitude": 169.95
    },
    "id": {
        "authority": "EPSG",
        "code": 9315
    },
    "remarks": "Derived at 205 control points. Mean offset 0.254m, standard deviation 0.039m, maximum difference from mean 0.11m. Supersedes NZVD2016 height to Dunedin-Bluff 1960 height (1) (code 7863) after change of grid file format."
}

<?xml version="1.0" encoding="utf-8"?>
<Map srs="+proj=vgridshift +grids=nz_linz_dublht1960-nzvd2016.tif +multiplier=1">
	<Layer srs="+proj=vgridshift +grids=nz_linz_dublht1960-nzvd2016.tif +multiplier=1">
	</Layer>
</Map>

INSERT into spatial_ref_sys (srid, auth_name, auth_srid, proj4text, srtext) values ( 9315, 'EPSG', 9315, '+proj=vgridshift +grids=nz_linz_dublht1960-nzvd2016.tif +multiplier=1', 'None');