Your on-board gps-based fms/rnav unit is ifr certified under tso-c129() or tso- your destination is below minimums for the gps rnav approach and you proceed to your filed alternate. you know that: . gps units certified under tso-c129() or tso-c196() are not authorized for alternate approach requirements; subsequently, you must use an approach procedure based on ground-based navaidsb. once diverted to the alternate airport, you may fly a gps-based approach as long as there is an operational ground-based navaid and appropriate airborne receiver for use as a backupc. if your air-craft is equipped with a second tso-c129() certified gps as a backup in place of a ground-based navaid receiver, you may complete the approach even if the iap is based on ground-based navaids