Here is a link: www.globalfishingwatch.org/data-blog/circling-above-point-reyes which was called to my attention because of the connection to AIS ( a system that ships use to keep track of positions ) and the changes recently made to allocations in frequency for 5G ( or 4G, LTE? ) communication by the F.C.C. Ref: https://lnkd.in/gdF-a8C c4isrnet.com Now there are a few different theories: 1. Someone having fun sending silly info to the AIS database server ( this sounds pretty far-fetched, because it would require a lot of work to build 'circular tracks' of dis-information ). 2. Intentional 'spoofing', because at least three of the ships were sailing in waters where the Ukraine government may have had cause to believe that other parties had motive and equipment. Typical equipment might include "GPS Constellation Factory Testers" which can record and/or play back signals used to test new GPS equipment for the ability to reject false signals. Older GPS systems did not include the newer constellations. 3. Non-intentional 'spoofing' involving harmonics or fundamental overload of GPS receivers by 5G/ 4G LTE base stations, whether or not in 'set-up' ( initial installation ) status. 4. Poor integration of various systems which contribute to AIS, eg. Satellite and LTE systems. 5. Other theories ( post 'em here... ) ??? Yes, this is not amateur radio per se. Yet since many enjoy APRS, it should be of interest to those who follow developments in electronic navigation. One example is DGPS ( Differential GPS ), where reference stations on earth are used for corrections to satellite-based signals.