Coordinate reference system

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://opendevelopmentstandards.org/schema/1.0.0-rc.2/core/Crs.json",
  "title": "Coordinate reference system",
  "description": "How to read coordinates and heights (ISO 19111): the horizontal system, the vertical system that heights refer to and the epoch of the coordinates. A crs names its system by a registry code, or holds the full definition of the system. Coordinates are in GeoJSON order (x, y) for every system: easting then northing, or longitude then latitude. When a record has no crs, coordinates are WGS 84 longitude and latitude (EPSG:4326).",
  "type": "object",
  "properties": {
    "epsgCode": {
      "type": "integer",
      "minimum": 1,
      "description": "The EPSG code of the horizontal system, for example 4326 or 32612. It means the same as a `code` of `EPSG:` and this number."
    },
    "code": {
      "type": "string",
      "pattern": "^[A-Z][A-Z0-9_]*:[A-Za-z0-9_.-]+$",
      "description": "The code of the system in a registry, as `<authority>:<code>`, such as `EPSG:3400` or `ESRI:102184`. The code of a compound system names the horizontal system and the vertical system together."
    },
    "name": {
      "type": "string",
      "minLength": 1,
      "description": "The name of the system, as its registry or its definition writes it, such as `NAD83(CSRS) / Alberta 10-TM (Forest)`."
    },
    "wkt": {
      "type": "string",
      "minLength": 1,
      "description": "The full definition of the system as WKT 2 (ISO 19162). Use it when no registry holds the system, such as a site grid."
    },
    "projjson": {
      "type": "object",
      "x-ods-open": true,
      "description": "The full definition of the system as PROJJSON."
    },
    "verticalDatum": {
      "type": "string",
      "enum": [
        "EGM96",
        "EGM2008",
        "WGS84",
        "NAVD88",
        "CGVD2013",
        "AHD",
        "local"
      ],
      "description": "The datum that absolute heights refer to.",
      "x-ods-options": [
        {
          "value": "EGM96",
          "title": "EGM96",
          "description": "Earth Gravitational Model 1996 geoid."
        },
        {
          "value": "EGM2008",
          "title": "EGM2008",
          "description": "Earth Gravitational Model 2008 geoid."
        },
        {
          "value": "WGS84",
          "title": "WGS 84 ellipsoid",
          "description": "Heights above the WGS 84 ellipsoid."
        },
        {
          "value": "NAVD88",
          "title": "NAVD 88",
          "description": "North American Vertical Datum of 1988."
        },
        {
          "value": "CGVD2013",
          "title": "CGVD2013",
          "description": "Canadian Geodetic Vertical Datum of 2013."
        },
        {
          "value": "AHD",
          "title": "AHD",
          "description": "Australian Height Datum."
        },
        {
          "value": "local",
          "title": "Local",
          "description": "A local datum; the record says which in its description."
        }
      ]
    },
    "verticalCode": {
      "type": "string",
      "pattern": "^[A-Z][A-Z0-9_]*:[A-Za-z0-9_.-]+$",
      "description": "The code of the vertical system that absolute heights refer to, as `<authority>:<code>`, such as `EPSG:6647` for CGVD2013(CGG2013) heights. Use it when `verticalDatum` does not list the system, or to name the geoid model."
    },
    "coordinateEpoch": {
      "type": "number",
      "description": "The date that the coordinates are true for, as a decimal year, such as 2010.0 (ISO 19111, coordinate epoch). A system that is not fixed to the ground, such as WGS 84 or ITRF2020, needs it: the ground moves in such a system by centimetres each year."
    },
    "zone": {
      "type": "string",
      "description": "The zone, when the system has zones and its code does not name one (for example 12N)."
    }
  },
  "anyOf": [
    {
      "properties": {
        "epsgCode": true
      },
      "required": [
        "epsgCode"
      ]
    },
    {
      "properties": {
        "code": true
      },
      "required": [
        "code"
      ]
    },
    {
      "properties": {
        "wkt": true
      },
      "required": [
        "wkt"
      ]
    },
    {
      "properties": {
        "projjson": true
      },
      "required": [
        "projjson"
      ]
    }
  ],
  "patternProperties": {
    "^x-": {}
  },
  "unevaluatedProperties": false,
  "examples": [
    {
      "epsgCode": 4326,
      "verticalDatum": "CGVD2013"
    },
    {
      "epsgCode": 32612
    },
    {
      "code": "EPSG:4617",
      "name": "NAD83(CSRS)",
      "verticalDatum": "CGVD2013",
      "verticalCode": "EPSG:6647",
      "coordinateEpoch": 2010
    },
    {
      "code": "ESRI:102184"
    },
    {
      "name": "Site grid",
      "wkt": "ENGCRS[\"Site grid\",EDATUM[\"Site datum\"],CS[Cartesian,2],AXIS[\"east (E)\",east],AXIS[\"north (N)\",north],LENGTHUNIT[\"metre\",1]]"
    }
  ],
  "x-ods-status": "draft",
  "x-ods-kind": "datatype",
  "x-ods-module": "core",
  "x-ods-changes": {
    "0.1.0": "First version."
  }
}