Pxtyson Posted December 29, 2006 Share Posted December 29, 2006 Why does my 60csx log movement when it is motionless on my desk for awhile? Quote Link to comment
bkrownd Posted December 29, 2006 Share Posted December 29, 2006 Why does my 60csx log movement when it is motionless on my desk for awhile? Assuming you have reception, it shows you in a different place than you are now? Quote Link to comment
+BlueDeuce Posted December 29, 2006 Share Posted December 29, 2006 Civilian gps accuracy is measured in feet not millimeters It’s going to dance. Quote Link to comment
Pxtyson Posted December 29, 2006 Author Share Posted December 29, 2006 it says that i have logged 80 meters in 20 minutes Quote Link to comment
+TotemLake Posted December 29, 2006 Share Posted December 29, 2006 Your GPS is experiencing what was earlier termed as the bumble bee dance. Even though you are sitting still, the geometric position of the satellites measuring your position are not. They are continuously moving requiring a new time signal to your position which must be recalculated. This is what your EPE (Estimated Position Error) is about. Quote Link to comment
bkrownd Posted December 29, 2006 Share Posted December 29, 2006 it says that i have logged 80 meters in 20 minutes It shows you 80 meters away from your known location? Or are you talking about the odometer only? Please be specific. Quote Link to comment
+pppingme Posted December 29, 2006 Share Posted December 29, 2006 Why does my 60csx log movement when it is motionless on my desk for awhile? Are you in California? Is it showing your moving West?? Thats not good, hope you have your life jacket ready... Seriously though, you said its on your desk, that probably means your not getting a good view of the sat's. As others have stated, because the sat's are constantly moving, and your recomputing your position based on that, some movement is normal, and its probably worse because your inside, and aren't getting "good geometry" with the sat's. Ideally you should have sat's on different sides of you, but if your inside, they are probably all on one side (your near an east window, so most of the sat's you see are east of you). This makes for worse accuracy than normal Quote Link to comment
+Team Trail Walker Posted December 29, 2006 Share Posted December 29, 2006 6.67 centimetres x 1200 seconds (calculation rate for sake of argument) = 80.4 Meters Not too bad! 6 meters (3 meter EPE) x 1200 seconds = 7.2 kilometers (assuming worst case) Ouch! Quote Link to comment
+pdxmarathonman Posted December 29, 2006 Share Posted December 29, 2006 There has been a copious amount of discussion regarding the "wandering" that the unit does while sitting on a desk with great reception of the satellites. The earlier descriptions of why are good ones, and the reason some others don't wander is because they do averaging by default which minimizes the variation. Quote Link to comment
robertlipe Posted December 30, 2006 Share Posted December 30, 2006 It's a well discussed trait of that family of products. See the last two sections ("My Ghost" and "When in Roam") at http://www.mtgc.org/robertlipe/showdown/ Quote Link to comment
+BlueDeuce Posted December 30, 2006 Share Posted December 30, 2006 Are you in California? Is it showing your moving West?? Thats not good, hope you have your life jacket ready... That was worth a good chuckle. Quote Link to comment
Pxtyson Posted December 30, 2006 Author Share Posted December 30, 2006 okay guys i am just doing a test right now and in 3 min 17 seconds of sitting completely still on my desk with a 9m accuracy i have had it move at 4.9kmh and also moved 13m Quote Link to comment
+GPSOkie Posted December 30, 2006 Share Posted December 30, 2006 okay guys i am just doing a test right now and in 3 min 17 seconds of sitting completely still on my desk with a 9m accuracy i have had it move at 4.9kmh and also moved 13m If it is on your desk, I would assume that you are not getting the best reception. A more accurate test would be to set it outside with a clear view of most of the sky. It will still wander around a bit. That is normal. If it make 20-30 6 foot jumps over 30 minutes, it will add up quickly. But again, that is normal. Quote Link to comment
robertlipe Posted December 30, 2006 Share Posted December 30, 2006 I've heard the "at your desk" point before. I've taken the 60csx outside with a nearly horizon-to-horizon view - and with and without an external antenna at that - and observed the same trait. These units simply don't do position averaging and if you set them perfectly still, its best guess of your position will jitter 6 feet this way and 7 feet that way and 8 feet that way every few seconds. Over your 30 minutes, that few feet of jitter adds up to a substantial distance. Quote Link to comment
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