When the first satellite weather receiver was installed in my Baron several years ago the local FAA inspectors insisted that the radio shop put a placard near the display commanding that “Satellite Weather Information Not To Be Used For IFR Navigation” before they would approve the system. I thought that was about the stupidest placard I had seen in an airplane. That early system delivered by low, Earth-orbiting satellites was not reliable enough to use for weather information, much less navigation. Plus, how do you navigate using weather information sent by satellite anyway?
Well, maybe that FAA inspector was prescient. Not long ago I did use the Nexrad radar image sent to my airplane by XM Weather to navigate my way back home to New York from Wichita. At least I used the XM information to know where not to go, which may be the opposite of navigation, which, I think, is knowing where you are, where you want to go and how to get there.
