EDIT: I read some other, more complete sources, it looks like jamming.
Disclaimer: I worked at Trimble Nav Ltd. in the radio group.
In general, GPS errors could also be caused by:
- PRC MIL jamming non-military non-BeiDou positioning systems to prevent drone or cruise missile attacks
- US MIL increasing Selective Availability (SA) on or disabling the unencrypted signal for a region
- Physical obstructions: trees, buildings, etc.
You'd think huge ships would have laser ring gyro INS and GLONASS/Galileo/BeiDou as a backup? Depending on a locally-jammable, unencrypted data monoculture (GPS) for multiple critical systems is a SPOF and insane.
Selective Availability is on its way out. In addition to being disabled for 20 years, supposedly the new 3rd generation GPS satellites were built without the capability.
JDAMs apparently have had an inertial system for backup for some time. MEMS gyros are good enough to guide from release to target. DARPA has quietly been working on compact, low-cost guidance without GPS for a while.[1] Doesn't seem to have filtered down to the commercial market yet, and that's probably not an accident.
Disclaimer: I worked at Trimble Nav Ltd. in the radio group.
In general, GPS errors could also be caused by:
- PRC MIL jamming non-military non-BeiDou positioning systems to prevent drone or cruise missile attacks
- US MIL increasing Selective Availability (SA) on or disabling the unencrypted signal for a region
- Physical obstructions: trees, buildings, etc.
You'd think huge ships would have laser ring gyro INS and GLONASS/Galileo/BeiDou as a backup? Depending on a locally-jammable, unencrypted data monoculture (GPS) for multiple critical systems is a SPOF and insane.