Visual Glide Slope Indicator or Visual Glideslope Indicator (VGSI) is a ground device that uses lights to assist a pilot in landing an airplane at an airport.
There are several different types of VGSIs: In the United States, the Federal Aviation Administration includes VGSI information in its Chart Supplement (formerly the Airport/Facility Directory) publication.
The VGSI, if installed, is listed immediately after each runway and is coded to indicate the type and specific implementation.
For example, Chicago Executive Airport (KPWK) located in Wheeling, IL has runway 16.
The various VGSI codes and their descriptions can be found in the "VISUAL GLIDESLOPE INDICATORS" section of the Directory Legend in the Chart Supplement.