(2)
Visual ground aids, such as Visual Approach Slope Indicator's, which provide vertical guidance for VFR approach or for the visual portion of an instrument approach and landing.

(3)
PAR (ON/ABOVE/BELOW) - Used by Air Traffic Control to inform an aircraft making a Precision Approach Radar approach of its vertical position (elevation) relative to the descent profile. The terms "slightly" and "well" are used to describe the degrees of deviation; e.g., "slightly above Glide Path.” Trend information is also issued with respect to the elevation of the aircraft and may be modified by the terms “rapidly” and “slowly;” e.g., “well above Glide Path, coming down rapidly.” (See Precision Approach Radar/PAR)

GLIDESLOPE/GLIDEPATH INTERCEPT ALTITUDE - The minimum altitude to intercept the glide slope/path on a precision approach. The intersection of the published intercept altitude with the glide slope/path, designated on government charts by the lightning bolt symbol, is the precision Final Approach Fix; however, when Air Traffic Control directs a lower altitude, the resultant lower intercept position is then the Final Approach Fix. (See Final Approach Fix, Segments of an Instrument Approach Procedure)
GLOBAL POSITIONING SYSTEM (GPS) - A space-based radio positioning, navigation, and time-transfer system. The system provides highly accurate position and velocity information, and precise time, on a continuous global basis, to an unlimited number of properly equipped users. The system is unaffected by weather, and provides a worldwide common grid reference system. The GPS concept is predicated upon accurate and continuous knowledge of the spatial position of each satellite in the system with respect to time and distance from a transmitting satellite to the user. The GPS receiver automatically selects appropriate signals from the satellites in view and translates these into three-dimensional position, velocity, and time. System accuracy for civil users is normally 100 meters horizontally.