czml-reference-properties

CZML Reference Properties

• A reference string has the form "<entityId>#<propertyPath>", e.g. "leadVehicle#position" or "labelEntity#label.outlineColor" (dotted path into a nested graphics property).
• Single-value reference: any property that normally takes a literal value can instead take { "reference": "<entityId>#<propertyPath>" }, e.g. "position": { "reference": "leadVehicle#position" } so this entity always tracks another entity's (possibly time-varying) position, or "material": { "solidColor": { "color": { "reference": "labelEntity#label.outlineColor" } } } so a shape's fill color follows another entity's color property.
• Array of references (e.g. building a polygon's corner positions entirely from other entities' positions, so the shape updates as those entities move): "positions": { "references": ["vertexA#position", "vertexB#position", "vertexC#position"] } — each referenced property must itself resolve to a single position.

Example: a polygon whose corners track three other moving entities

[
  { "id": "document", "name": "Reference positions", "version": "1.0" },
  {
    "id": "vertexA",
    "position": {
      "epoch": "2026-01-01T00:00:00Z",
      "cartographicDegrees": [0, -90, 30, 0, 3600, -89.9, 30, 0]
    }
  },
  {
    "id": "vertexB",
    "position": {
      "epoch": "2026-01-01T00:00:00Z",
      "cartographicDegrees": [0, -89.9, 30.1, 0, 3600, -89.8, 30.1, 0]
    }
  },
  {
    "id": "vertexC",
    "position": {
      "epoch": "2026-01-01T00:00:00Z",
      "cartographicDegrees": [0, -90, 30.1, 0, 3600, -89.9, 30.1, 0]
    }
  },
  {
    "id": "tracking-polygon",
    "polygon": {
      "positions": { "references": ["vertexA#position", "vertexB#position", "vertexC#position"] },
      "material": { "solidColor": { "color": { "rgba": [255, 0, 0, 128] } } }
    }
  }
]