A Visual Docking Guidance System (VDGS) is a stand guidance system that usually consists of an Azimuth Guidance for Nose-in Stands (AGNIS) along with Parallax Aircraft Parking Aid (PAPA).
The light bars on the AGNIS display one of the following signals:
- There are two bars
- If both are green, they indicate correct alignment
- If one is red, they need to steer away from the side that has turned green