Figure 6-1. Area navigation (RNAV) receivers.  The capabilities of airborne navigation databases depend  largely on the way they are implemented by the avionics  manufacturers. They can provide data about a large  variety of locations, routes, and airspace segments for use  by many different types of RNAV equipment. Databases  can provide pilots with information regarding airports,  air traffic control (ATC) frequencies, runways, and special  use airspace. Without airborne navigation databases,  RNAV would be extremely limited. In order to understand  the capabilities and limitations of airborne navigation  databases, pilots must understand the way databases  are compiled and revised by the database provider and  processed by the avionics manufacturer. Vital to this  discussion is understanding of the regulations guiding  database maintenance and use.  There are many different types of RNAV systems certified  for instrument flight rules (IFR) use in the National Airspace  System (NAS). The two most prevalent types are GPS and  the multisensory FMS. [Figure 6-2] A modern GPS unit  accurately provides the pilot with the aircraft’s present  position; however, it must use an airborne navigation  database to determine its direction or distance from  another location. The database provides the GPS with  6-2 