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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. 

## Local Area Augmentation System (LAAS) 

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] 

