The laser-sharp GPS is the new tool for global positioning.

  The laser-sharp GPS is the new tool for global positioning. 

Laser retroreflector arrays (LRAs) are laser-based systems that give extended accuracy for the GPS. The system base is in reflectors that are on the ground. Then the LRA satellite aims the laser ray at that reflector. This kind of system can used to calibrate the system. When the laser ray impacts a very high-accuracy positioned mirror the laser system can calibrate the GPS satellite. 

If those reflectors are in the same position, the satellite can measure differences in those reflector's vertical and horizontal positions. The laser reflector can also connected to a man or vehicle. That allows the laser system to locate the person or vehicle.  Or the ground station group can position the satellite at the orbiter using lasers. That gives the system ultimate accuracy. 

"GPS satellites support Earth measurements by relaying information to other satellites. Laser retroreflector arrays (LRAs) are improving this process, enhancing the accuracy of geodesy – the study of Earth’s shape and changes. LRAs enable precise distance measurements, essential for monitoring global phenomena like sea level rise and tectonic shifts. (Artist’s concept.) Credit: SciTechDaily.com" (ScitechDaily.com/Laser Sharp GPS: How NASA’s Reflectors Are Redrawing Our World)

The other version uses lasers as the GPS to aim the active laser upward. That laser can also used as laser sight. The laser sights are multi-use tools, that can be used as laser microphones, laser sights, target indication, and laser communication tools. Systems can used to point the person or vehicle, and laser can send an IFF (Identification Friend or Foe) signal for incoming helicopters or aircraft. 

Then photo recon satellite, drone or aircraft, or earth observation satellite (KH13, Landsat) detects that laser ray. That kind of system can also transmit information like encoded data messages to those satellites. That allows engineers to connect communication tools for this kind of system. The laser-based communication is always harder to jam than radio-based systems. 

And even if somebody jams the system, the jammer must use the same frequency as the jammed communication tool. Then the jamming laser ray must have a higher energy level than the communication laser. That makes the jamming laser turn the laser ray that transports data to satellites in another direction. But the satellites and other optical systems can see the point, where the jamming station is. 

The jammer laser must cut the communication laser using very high accuracy. And if the first communication laser uses IR light the other can use UV frequency. That makes it harder to cut the data line. And of course, those satellites can use multi-band systems. Like different wavelength coherent radio waves and optical systems. 

https://scitechdaily.com/laser-sharp-gps-how-nasas-reflectors-are-redrawing-our-world/