Grey areas: Few people live there and none have set up a public ADS receiver. And/or no planes flying in the area. https://gpsjam.org/faq/#why-arent-there-red-o

Grey areas: Few people live there and none have set up a public ADS receiver. And/or no planes flying in the area. https://gpsjam.org/faq/#why-arent-there-red-or-green https://gpsjam.org/faq/#why-arent-there-red-or-green Red areas: Military experiments and exercises, probably. https://gpsjam.org/faq/#what-can-cause-aircraft-to-report-low-accuracy https://gpsjam.org/faq/#what-can-cause-aircraft-to-report-lo...