Overland1 Posted November 4, 2003 Share Posted November 4, 2003 A few months ago, while driving on I-90 from Geneva, NY to Rochester, NY, I noticed my Vista was displaying abnormally high speeds and distances, as well as showing me as being near Worcester MA . This happened again yesterday morning near the same location of the previous occurrence. I eventually powered the Vista down and back up, and it worked OK afterward, but the Max Speed displayed was 1229 MPH. The Distance showed >600 miles for a 250-mile trip, and the map (before I turned it off and on again) showed me as being near Lockport, NY. I called Garmin and their rep advised me to send it in under warranty for diagnosis and repair. The firmware is at the latest level, and the map is Mapsource 5 (latest update). One person suggested that the E-Z Pass system at the toll booth may have caused the problem..... any ideas on this? I Roger your vector, Victor...... Over. Quote Link to comment
+mrp Posted November 4, 2003 Share Posted November 4, 2003 This sounds like a classic case of multipath reception. Basically, if the receiver has a minimal solution (just 4 satellites), and the signal of one of those sats is reflecting off some other object (i.e. a nearby cliff, etc.) Then this kind of thing happens. The doppler signatures area all wrong, so the speed is screwed up, and it also usually thinks you're several hundred miles away from your actual location. This is moderately rare, and it's not something that is due to anything wrong with your GPSR. Units with patch antennas are less suceptible to this, since reflected signals are pretty weak (one reason they used microwaves, they don't reflect or refract very well.) Using an amplified antenna may make this more likely (since the weak reflected signals get amplified.) Generally, as soon as it has an overspecified solution (more than 4 sats locked), then this won't happen. It happened to a friend of mine while taking an Alaskan cruise. He was on a cruise ship in the inner passage doing about 20 kts (about 23 mph), but for 5 track points, his GPSR put in in the middle of the northern pacific. The first couple of trackpoints show him doing about 930mph (about mach 1.3), but the last two show him doing 247073 mph and 701267 mph repectively. The tracklog lists 339 miles covered in 28 seconds.. or an average of about 43,500 mph. About that time his GPSr (Garmin GPSMap 76S) finally figured out that the solution it had didn't make sense and lost lock. :-) -- Pneumatic [This message was edited by Pneumatic on November 04, 2003 at 09:37 PM.] Quote Link to comment
vagabond Posted November 5, 2003 Share Posted November 5, 2003 It happened once with my Magellan gold, in a steep canyon under heavy tree cover. Showing me about 50 miles away and doing about 300 mph, this happened almost 2 years ago and hasn't happened since. For what its worth All who look are not lost Quote Link to comment
Overland1 Posted November 20, 2003 Author Share Posted November 20, 2003 Update: I sent the unit in as recommended by Garmin, and they replaced the unit. The new one seems to be more sensitive with accuracy reading in the mid-teens more frequently. They said in their note that it was not picking up satellites reliably.... must be they duplicated the problem or were aware of it anyway (I sent it in without resetting the data). I plan to do more testing with the Vista to see if the problem is now corrected, or if, as explained above, it still may occur again. More to follow as results are available. Quote Link to comment
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