So this pertains to jamming so strong that traditional jam-proof GPS that uses signal phase shift to weed out GPS signals coming from "wrong" directions, are in

So this pertains to jamming so strong that traditional jam-proof GPS that uses signal phase shift to weed out GPS signals coming from "wrong" directions, are insufficient? 100db attenuation of jamming signal has been achieved around 15 years ago with those. In the air, there are always more GPS satellites visible than necessary. So jam-proofing through signal processing methods is the way to go.