jshell Posted June 30, 2003 Share Posted June 30, 2003 My SporTrak Map is always 3 minutes off from the real time. I manually set the time to the actual time but as soon as it interacts with the GPS satellites, it resets the time to 3 minutes off. Has anyone else seen this? I know GPS satellites have to be accurate to billionths of a second for accurate positioning. I have checked the time against Atomic Clock signal time and other time beacons. Any ideas? Quote Link to comment
+TeamCNJC Posted June 30, 2003 Share Posted June 30, 2003 Do a reset (clear all memory). That should fix it. -Craig/TeamCNJC ... Two roads diverged in a wood, and I-- I took off through the thorns, chest high, ... Quote Link to comment
+Searching_ut Posted June 30, 2003 Share Posted June 30, 2003 Your GPS unit doesn't actually use it's internal clock for position calculations because it isn't accurate enough. They use a pretty fancy way of computing it instead. The clock is simply to give the receiver a good idea of where to look initially to find the sats. As for the accuracy problem, the reset mentioned by TeamCNJC will take care of it. I havn't been able to figure out what all can cause the error however. Seems updating the firmware can do it, but evidently there is something else that can cause it as well being as how both of my sportrak maps have developed clock errors periodically. I just started using a program called TopoFusion that allows me to play back multiple tracks at the same time. It works great for comparing different receivers, but I've found that the clock problem messes things up for most of my old tracks. Quote Link to comment
+graewulf Posted July 1, 2003 Share Posted July 1, 2003 quote:Originally posted by jshell:My SporTrak Map is always 3 minutes off from the real time. I manually set the time to the actual time but as soon as it interacts with the GPS satellites, it resets the time to 3 minutes off. Has anyone else seen this? I know GPS satellites have to be accurate to billionths of a second for accurate positioning. I have checked the time against Atomic Clock signal time and other time beacons. Any ideas? OK, stupid question time.. are you sure your clocks are accurate? were they set from the atomic clocks? I have an atomic clock (radio set) in the house i use as my master clock. I just checked my sporttrak map against the atomic clock - it's off by 5 seconds.... Quote Link to comment
+Searching_ut Posted July 2, 2003 Share Posted July 2, 2003 If you mean the clocks we're comparing the GPS units too yes. As mentioned, you can change the time in the unit, but once it locks onto the sat signal again, it resets itself to the wrong signal. The sats broadcast a very accurate time signal from atomic clocks that are closely monitored by ground tracking stations. It the clocks start to become out of spec, they have additional clocks in the sats they can switch to. As for the Sportrak, once you do a complete reset, it fixes itself and is accurate again once it locks on. My biggest question is what changes in the sportraks software, and what is it that triggers the unit to offset the time. Quote Link to comment
+TeamCNJC Posted July 2, 2003 Share Posted July 2, 2003 quote:Originally posted by Searching_ut:As for the Sportrak, once you do a complete reset, it fixes itself and is accurate again once it locks on. My biggest question is what changes in the sportraks software, and what is it that triggers the unit to offset the time. I don't know what specifically causes the time shift, but I noticed it after doing a basemap switch using menu-86. As I posted earlier, a complete reset fixed the issue. -Craig/TeamCNJC ... Two roads diverged in a wood, and I-- I took off through the thorns, chest high, ... Quote Link to comment
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