Investigate anti-jamming for GNSS module

[louisbertrand]

The U-Blox manual mentions anti-jamming features. Can they be integrated into the Zen firmware.
This may be important for data collectors in Ukraine.
Connect with Pavlo for additional information.

See Ublox manual sections...
14.2 Jamming/Interference Indicator
14.3 Jamming/Interference Monitor
15.x Spoofing Detection

[louisbertrand]

Conversation with Pavlo Apr 23: "crazy" shifts in reported location of fixed devices seems to occur with air raid alerts. See Grafana: https://grafana.safecast.cc/d/DFSxrOLWk/safecast-device-details?orgId=1&from=1711838230023&to=1712801145911&var-device_urn=geigiecast:62400
Could correlate reported data points with dataset of Ukraine air raid alerts:
https://github.com/Vadimkin/ukrainian-air-raid-sirens-dataset

To retrieve spoofing and jamming from UBX protocol:
Spoofing: 32.18.20 UBX-NAV-STATUS (0x01 0x03) Receiver Navigation Status
Offset 7 uint8_t flags2 bits[4:3] spoofDetState 0: Unknown or deactivated; 1: No spoofing indicated; 2: Spoofing indicated; 3: Multiple spoofing indications
Note that the spoofing state value only reflects the detector state for the current navigation epoch. As spoofing can
be detected most easily at the transition from real signal to spoofing signal, this is also where the detector is
triggered the most. I.e. a value of 1 - No spoofing indicated does not mean that the receiver is not spoofed, it
simply states that the detector was not triggered in this epoch.
Jamming: 32.17.4 UBX-MON-HW (0x0A 0x09), Hardware Status
Offset 22 uint8_t flags bits[3:2] jammingState Jamming interference monitor: 0=unknown or disabled; 1=OK; 2=warning, fix is OK; 3=critical, no fix.
Offset 45 uint8_t jamInd CW Jamming scaled 0--255.
jammingState (offset 22) applies to both CW and broadband interference.
JamInd (offset 45) indicates the presence of a narrow band (CW) signal that causes the receiver front-end automatic gain control (AGC) to reduce the input gain, thus desensitizing the input. It is not necessarily malicious, it may simply be the proximity of a powerful transmitter. To "calibrate" the jamming threshold, the device must be configured in a non-jamming environment.
32.11.14 UBX-CFG-ITFM (0x06 0x39) Jamming/Interference Monitor configuration
Configure the threshold above normal at which narrowband or broadband interference is detected in the receiver.