There are secret mountains under our feet.

Gravitational and seismic measurements uncover the secret mountains under our feet. Those mountains are the thicker areas in the magma. And those mountains are the thing that can use as the tool for next-generation navigation systems. The gravitational measurements can uncover the internal structures of planets, that are deep underground. 

The measurements that prove that the internal structures of Earth are not homogenous are opening roads to benefit those structures in navigation. There are conditions in which GPS satellites or even the compass are unable to operate. That requires that the place of those structures is fixed or their location is precisely known. 

"Seismic waves from earthquakes in the southern hemisphere sample the ULVZ (Ultra-Low Velocity Zone) structure along the Earth’s CMB and are recorded by sensors in Antarctica. Credit: Edward Garnero and Mingming Li, Arizona State University." (ScitechDaily.com/Seismic Sleuths Reveal Earth’s Secret Mountains: A Hidden World Beneath Our Feet)

Those places are the deep underground tunnels and extremely powerful electromagnetic fields. The internal structures on Earth are allowing the creation of the gravitational TERCOM system that can navigate in the cases that the TERCOM (Terrain Contour Matching) cannot operate. 

Jamming the TERCOM system can happen by making a plasma field between the user of TERCO and the ground. There is also a possibility that artificial floods or changes in the routes of rivers can use to jam that system. The selected method can base on the tools that the TERCOM system uses. 

If TERCOM uses the optical systems flooding of rivers can protect the target. There is also the possibility that the satellite follows the flight of the user of the TERCOM by benefiting the laser that is the back of the aircraft or missile. This is the semi-active version of the TERCOM system. The system uses an optical seeker that is in the recon satellite, and then the satellite aims the TERCOM to the right course. The satellite sees the missile or aircraft against the map.