PPL Study books
Re: And remember, GPS is susceptible to jamming and interference (my ar5e)
I seem to remember seeing a Notam early last year regarding the 'testing' of the satellites that would render GPS signals unreliable in the midlands for a period of time. I would imagine 'testing' means the Americans were jamming and interfering with 'their' satellites.
If that was the case, anybody flying using GPS only would have had a problem, especially in poor visibility.
So it is a good idea to check notams before flying, it is recommended and with todays technology (iPhones, iPads, android phones, computers, laptops, landlines, etc) it's not that difficult.