{
  "name": "crs_to_authid",
  "type": "function",
  "groups": ["CRS"],
  "description": "Returns the authority ID string for a coordinate reference system.",
  "arguments": [{
    "arg": "crs",
    "description": "crs value"
  }],
  "examples": [{
    "expression": "crs_to_authid(crs_from_text('PROJ:+proj=merc +a=6378137 +b=6378137 +lat_ts=0 +lon_0=0 +x_0=0 +y_0=0 +k=1 +units=m +nadgrids=@null +wktext +no_defs +type=crs'))",
    "returns": "'EPSG:3857'"
  }],
  "tags": ["crs", "epsg", "authid"]
}