CompuServe Messages

Hi, Rob, Lanny, and others– In another message, Rob mentions a "mask angle" setting on a GPS unit. It seems using this setting carefully might avoid the problem of signals being reflected off mountains and whatnot. If the mask angle is set higher than any nearby mountains, many reflections should be rejected. I am assuming the mask angle is a setting that causes signals from GPS satellites too close to the horizon to be ignored. If the GPS unit can actually detect the direction of the signal (phased array detector with a sensor for the orientation of the unit??), this should work quite well. But I am guessing the unit really "listens" to the satellite for info on where it is, and then decides whether or not to ignore it. This would leave it unable to distinguish reflected and direct signals from the same satellite, but reflections from satellites not in view would be rejected, and satellites close to overhead are likely to send reflections to the observer only via shallow reflection angles, which I am guessing are less efficient and thus less troublesome. If this is impractical, I wonder if GPS units allow one to determine which satellites it will pay attention to. "This satellite's signal looks fuzzed up, so I will just push the reject button…" I am largely ignorant of GPS; am I barking up the wrong tree, folks? –Doug