Definition of "temporal_cs"

NOTE: Markdown does not support highlighting in color, so bold/italic has been used to highlight the material being discussed. This issue is extracted from the document submitted by Roger Lott at https://github.com/opengeospatial/CRS-JSON-Encoding/blob/main/ProjJson%20v0-7%20RL%202024-06-16.docx for discussion at the CRS SWG meeting OGC held during the Montreal June 2024 TC meeting.

"temporal_crs": {
  "type": "object",

"allOf": [{ "$ref": "#/definitions/object_usage" }],

  "properties": {
    "type": { "type": "string", "enum": ["TemporalCRS"] },
    "name": { "type": "string" },
    "datum": { "$ref": "#/definitions/temporal_datum" },

"coordinate_system": { "$ref": "#/definitions/coordinate_system" }, STRIKE THIS LINE
"coordinate_system": {
"oneOf": [
{ "$ref": "#/definitions/temporalCount_cs" },
{ "$ref": "#/definitions/temporalDateTime_cs" }
{ "$ref": "#/definitions/temporalMeasure_cs" }
]
},

    "$schema" : {},

"scope": {},
"area": {},
"bbox": {},
"vertical_extent": {},
"temporal_extent": {},
"usages": {},

    "remarks": {},
    "id": {}, "ids": {}
  },

"required" : [ "name", "datum", "coordinate_system" ],

  "additionalProperties": false
},

"$comment": "[RL] See comment regarding usage under compound_crs."

"$comment": "[RL] A temporal CRS should be constrained to having a temporal_cs (one of temporalCount_cs, temporalDateTime_cs, or temporalMeasure_cs."

"$comment": "[RL] In 19111/Topic 2, a temporal CRS may have a datum ensemble rather than a datum. Not likely to be relevant for a tempral CRS so 19162/WKT2 spec does not offer the option. Should CRS JSON?"

Start with the proposed temporal_crs schema in this issue and the linked ProjJson v0-7 document. Review the referenced temporalCount_cs, temporalDateTime_cs, and temporalMeasure_cs definitions, then resolve whether coordinate_system should use them and whether datum ensembles or usage fields are permitted. Done means the temporal CRS requirements and schema questions have a documented decision.