I, on the other hand, would think that was extremely difficult, without using EMP from a nuke.
Quite.
Jamming "DC to daylight" would be difficult, if not impossible, especially for any period of time.
The amount of signal processing power you can cram into a small package these days is amazing. Throw in many modes of operation and a bit of Bayesian statistics and away you go! The "Assisted GPS" on modern phones uses known wifi and/or cell networks to help get quicker and more accurate fixes, I believe.