From Arda Industries:
A Mobile DME (Distance Measuring Equipment) station that you can position anywhere on your spaceport. It is a targetable object on the map that when placed near the runway, will allow you to know the location of the runway and the distance to it when this DME station is targeted.
Placing the DME near the touchdown zone of the runway is recommended, as well as renaming the DME station to a name that will help you remember what the object is. To move the station to its desired location, you can use the semi truck found in the link below:
Nikola One Semi Truck
To couple the trailer to the truck, simply back up the semi to the trailer (making sure the docking ports are lined up), switch to the trailer, and lower the landing gear.