How can GPS be affected by EW, and what are countermeasures?

• A. GPS can be jammed or spoofed; countermeasures include anti-jam receivers, encrypted signals, and use of alternative navigation aids.
• B. GPS is immune to EW; no countermeasures required.
• C. GPS can be enhanced by increasing signal strength from satellites; no countermeasures needed.
• D. GPS only affected by solar flares; encryption not used.

Answer: (A)

GPS can be affected by electronic warfare mainly through jamming and spoofing. Jamming floods the GPS frequencies with noise or a deceptive signal, making it hard for receivers to lock onto real satellites and leading to degraded accuracy or lost timing. Spoofing feeds counterfeit signals that mimic genuine satellites, potentially steering a user’s position and time to a false value. The best way to counter this is to address interference and deception on multiple fronts. Anti-jam receivers use wideband processing and adaptive antennas to suppress interfering signals and maintain lock on authentic satellites. Encryption of navigation signals, as used with military P(Y) and M-code, helps authenticate the signal and reduce spoofing risk, though civil GPS lacks such built‑in authentication. To preserve navigation when GPS is degraded, relying on alternative aids like inertial navigation systems, other GNSS constellations, and ground- or space-based augmentations provides continuity and cross-checks.