How does an airplane "point their GPS receiver at the ground" (for an extended period of time since a combined GNSS/INS positioning solution, which is what all airliners use at this point as far as I know, will need an extended signal loss to report decreased accuracy)?
Unfortunately some of the data that's most directly applicable to determining aircraft attitude, like roll, is optional and rarely sent by aircraft, but yes I'm sure you could do a decent job of inferring maneuvering from change in heading and vertical rate (especially if you're looking at ADS-B data with high temporal resolution vs., say, every 10-60 seconds.)
From the FAQ, it sounds like they simply presume that anywhere with multiple low NIC values is indicative of interference.
> The GPS interference data is derived from NIC (navigation integrity category) values that we receive as part of the ADS-B protocol. We mark regions as affected if a significant number of flights in that area report lowered NIC values.
on a pure radar scan, what would return of formation flying like this look like to a radar operator? is it just one large dot, or can they distinguish the number of planes in the formation?
