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such as takeoff, approach, and landing where important features such as terrain, obstacles, runways, and landmarks may be depicted on the SVS display. [Figure 5-15] During approach operations, the obvious advantages of SVS are that the digital terrain image remains on the pilot’s display regardless of how poor the visibility is outside. An SVS image can be displayed on either a head-down display or head-up display (HUD). Development efforts are currently underway that would combine SVS with a real-time sensor image produced by an EFVS. These systems will be known as Combined Vision Systems (CVS). 

## Synthetic Vision Guidance System (SVGS) 

SVGS is a combination of flight guidance display technology and high precision position assurance monitors. The SVGS flight instrument display provides a continuous, geo- 

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spatially correct, database driven, computer-generated synthetic depiction of the nearby topography, including obstacles, and a display of the landing runway. The SVGS display may be implemented on a head down Primary Flight Display, and/or a Head-Up Display (HUD). SVGS includes additional symbology, integrity and performance monitors and annunciations that enable low visibility operations. These additional monitors assure an accurate depiction of the external scene. An SVGS differs from an EFVS in that it does not produce a real-time image of the external scene. SVGS may not be used in lieu of natural vision. SVGS is intended to be used to increase situational awareness on the straight-in final approach segment of published instrument approaches and requires Special Authorization. 

## Enhanced Flight Vision System (EFVS) 

For an in-depth discussion regarding Enhanced Flight Vision Systems, see Chapter 4 of this handbook as well as AC 90-106 (current version). 

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## Combined Vision System Technology 

The FAA’s NextGen program will transform the NAS to accommodate a projected three-fold increase in air operations in the coming decade. Technological and systemic changes are being developed to significantly increase the capacity, safety, efficiency, and security of air operations in the NAS. The FAA will continue to evaluate, standardize and regulate emerging and enhanced technologies to ensure their safe and advantageous use in the NAS. One key capability envisioned to achieve these goals is the concept of equivalent visual operations (EVO), where flight operations continue irrespective of the actual weather conditions. One way EVO might be attained is by using a combined vision system (CVS) which combines real-time EFVS imagery with a database-derived synthetic rendering of surrounding terrain, obstacles, and flight environment, to provide a virtual visual flight depiction for the pilot. 

