Wide Area Reference Station  receives GPS signal  GPS  Satellites  1  Wide Area Reference Station  Wide Area Reference Station  data is sent to a Wide Area  Master Station for correction  GPS  Satellites  2  Wide Area Reference Station  Wide Area Master station uplinks corrected signal to GEO Synchronous Satellites  GUS  GEO Synchronous Satellites  3  Wide Area Reference Station  Wide Area Master station  GUS  GEO Synchronous Satellites sends updated WAAS signal to aircraft equipped with WAAS receivers  GEO Synchronous Satellites  4  Wide Area Augmentation System (WAAS)  Figure 9-29. WAAS satellite representation. of installing ground stations at each airport. A new class  of approach procedures, which provide vertical guidance  requirements for precision approaches, has been developed  to support satellite navigation use for aviation applications.  These new procedures called Approach with Vertical  Guidance (APV) include approaches such as the LNAV/ VNAV procedures presently being flown with barometric  vertical navigation.  LAAS is a ground-based augmentation system that uses a  GPS-reference facility located on or in the vicinity of the  airport being serviced. This facility has a reference receiver  that measures GPS satellite pseudo-range and timing and  retransmits the signal. Aircraft landing at LAAS-equipped  airports are able to conduct approaches to Category I level and  above for properly equipped aircraft.  [Figures 9-31  and  9-32] Local Area Augmentation System (LAAS) 9-33