@type t() :: %Sidereon.GNSS.QC.ObservationHeader{
  antenna: Sidereon.GNSS.QC.ObservationAntenna.t() | nil,
  antenna_delta_hen_m: {float(), float(), float()} | nil,
  approx_position_m: {float(), float(), float()} | nil,
  duration_s: float() | nil,
  marker_name: String.t() | nil,
  marker_number: String.t() | nil,
  marker_type: String.t() | nil,
  receiver: Sidereon.GNSS.QC.ObservationReceiver.t() | nil,
  time_of_first_obs: Sidereon.GNSS.QC.ObservationTime.t() | nil,
  time_of_last_obs: Sidereon.GNSS.QC.ObservationTime.t() | nil
}