EPSG:26921

BOUNDCRS[
    SOURCECRS[
        PROJCRS["NAD83 / UTM zone 21N",
            BASEGEOGCRS["NAD83",
                DATUM["North American Datum 1983",
                    ELLIPSOID["GRS 1980",6378137,298.257222101,
                        LENGTHUNIT["metre",1]]],
                PRIMEM["Greenwich",0,
                    ANGLEUNIT["degree",0.0174532925199433]],
                ID["EPSG",4269]],
            CONVERSION["UTM zone 21N",
                METHOD["Transverse Mercator",
                    ID["EPSG",9807]],
                PARAMETER["Latitude of natural origin",0,
                    ANGLEUNIT["degree",0.0174532925199433],
                    ID["EPSG",8801]],
                PARAMETER["Longitude of natural origin",-57,
                    ANGLEUNIT["degree",0.0174532925199433],
                    ID["EPSG",8802]],
                PARAMETER["Scale factor at natural origin",0.9996,
                    SCALEUNIT["unity",1],
                    ID["EPSG",8805]],
                PARAMETER["False easting",500000,
                    LENGTHUNIT["metre",1],
                    ID["EPSG",8806]],
                PARAMETER["False northing",0,
                    LENGTHUNIT["metre",1],
                    ID["EPSG",8807]]],
            CS[Cartesian,2],
                AXIS["(E)",east,
                    ORDER[1],
                    LENGTHUNIT["metre",1]],
                AXIS["(N)",north,
                    ORDER[2],
                    LENGTHUNIT["metre",1]],
            USAGE[
                SCOPE["Engineering survey, topographic mapping."],
                AREA["Canada between 60°W and 54°W - Newfoundland and Labrador; Nunavut; Quebec."],
                BBOX[38.56,-60,84,-54]],
            ID["EPSG",26921]]],
    TARGETCRS[
        VERTCRS["NAVD88 height",
            VDATUM["North American Vertical Datum 1988"],
            CS[vertical,1],
                AXIS["gravity-related height (H)",up,
                    LENGTHUNIT["metre",1]],
            USAGE[
                SCOPE["Geodesy, engineering survey, topographic mapping."],
                AREA["Mexico - onshore. United States (USA) - CONUS and Alaska - onshore - Alabama; Alaska; Arizona; Arkansas; California; Colorado; Connecticut; Delaware; Florida; Georgia; Idaho; Illinois; Indiana; Iowa; Kansas; Kentucky; Louisiana; Maine; Maryland; Massachusetts; Michigan; Minnesota; Mississippi; Missouri; Montana; Nebraska; Nevada; New Hampshire; New Jersey; New Mexico; New York; North Carolina; North Dakota; Ohio; Oklahoma; Oregon; Pennsylvania; Rhode Island; South Carolina; South Dakota; Tennessee; Texas; Utah; Vermont; Virginia; Washington; West Virginia; Wisconsin; Wyoming."],
                BBOX[14.51,172.42,71.4,-66.91]],
            ID["EPSG",5703]]],
    ABRIDGEDTRANSFORMATION["NAD83 to NAVD88 height (3)",
        METHOD["Geographic3D to GravityRelatedHeight (gtx)",
            ID["EPSG",9665]],
        PARAMETERFILE["Geoid (height correction) model file","g2003u03.bin"],
        USAGE[
            SCOPE["Derivation of approximate gravity-related heights from GNSS observations."],
            AREA["United States (USA) - CONUS north of 41°N and between 95°W and 78°W - Michigan and Wisconsin; Minnesota east of 95°W; Iowa north of 41°N and east of 95°W; Illinois, Indiana and Ohio north of 41°N; Pennsylvania north of 41°N and west of 78°W; New York west of 78°W."],
            BBOX[41,-95,49.37,-77.99]],
        ID["EPSG",10015],
        REMARK["Uses Geoid03 hybrid model. See information source for further information. Note: Source CRS is 2D, used in this application of the method as a pseudo-3D CRS."]]]

proj4.defs("EPSG:26921","+proj=utm +zone=21 +datum=NAD83 +units=m +no_defs +type=crs");

{
    "$schema": "https://proj.org/schemas/v0.7/projjson.schema.json",
    "type": "BoundCRS",
    "source_crs": {
        "type": "ProjectedCRS",
        "name": "NAD83 / UTM zone 21N",
        "base_crs": {
            "name": "NAD83",
            "datum": {
                "type": "GeodeticReferenceFrame",
                "name": "North American Datum 1983",
                "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": 4269
            }
        },
        "conversion": {
            "name": "UTM zone 21N",
            "method": {
                "name": "Transverse Mercator",
                "id": {
                    "authority": "EPSG",
                    "code": 9807
                }
            },
            "parameters": [
                {
                    "name": "Latitude of natural origin",
                    "value": 0,
                    "unit": "degree",
                    "id": {
                        "authority": "EPSG",
                        "code": 8801
                    }
                },
                {
                    "name": "Longitude of natural origin",
                    "value": -57,
                    "unit": "degree",
                    "id": {
                        "authority": "EPSG",
                        "code": 8802
                    }
                },
                {
                    "name": "Scale factor at natural origin",
                    "value": 0.9996,
                    "unit": "unity",
                    "id": {
                        "authority": "EPSG",
                        "code": 8805
                    }
                },
                {
                    "name": "False easting",
                    "value": 500000,
                    "unit": "metre",
                    "id": {
                        "authority": "EPSG",
                        "code": 8806
                    }
                },
                {
                    "name": "False northing",
                    "value": 0,
                    "unit": "metre",
                    "id": {
                        "authority": "EPSG",
                        "code": 8807
                    }
                }
            ]
        },
        "coordinate_system": {
            "subtype": "Cartesian",
            "axis": [
                {
                    "name": "Easting",
                    "abbreviation": "E",
                    "direction": "east",
                    "unit": "metre"
                },
                {
                    "name": "Northing",
                    "abbreviation": "N",
                    "direction": "north",
                    "unit": "metre"
                }
            ]
        },
        "id": {
            "authority": "EPSG",
            "code": 26921
        }
    },
    "target_crs": {
        "type": "VerticalCRS",
        "name": "NAVD88 height",
        "datum": {
            "type": "VerticalReferenceFrame",
            "name": "North American Vertical Datum 1988"
        },
        "coordinate_system": {
            "subtype": "vertical",
            "axis": [
                {
                    "name": "Gravity-related height",
                    "abbreviation": "H",
                    "direction": "up",
                    "unit": "metre"
                }
            ]
        },
        "id": {
            "authority": "EPSG",
            "code": 5703
        }
    },
    "transformation": {
        "name": "NAD83 to NAVD88 height (3)",
        "method": {
            "name": "Geographic3D to GravityRelatedHeight (gtx)",
            "id": {
                "authority": "EPSG",
                "code": 9665
            }
        },
        "parameters": [
            {
                "name": "Geoid (height correction) model file",
                "value": "g2003u03.bin",
                "id": {
                    "authority": "EPSG",
                    "code": 8666
                }
            }
        ],
        "id": {
            "authority": "EPSG",
            "code": 10015
        }
    }
}

<?xml version="1.0" encoding="utf-8"?>
<Map srs="+proj=utm +zone=21 +datum=NAD83 +units=m +no_defs +type=crs">
	<Layer srs="+proj=utm +zone=21 +datum=NAD83 +units=m +no_defs +type=crs">
	</Layer>
</Map>