What is this yellow pillar of light from the sky?
Solution 1:
Its a marker a squad leader or platoon leader can place. It shows up the map, minimap and in-game.
It acts as a waypoint that every player in the squad/platoon can see.
Solution 2:
This waypoint is marked by the game's mission system. You can toggle this on/off in options.
It's purpose is to help new players accomplish objectives such as outpost capture.
OP's image shows the bridge at Naum Ravine Overpass where the capture point is underneath the structure.