If you look closely at you GPS position, you will notice that it is almost always showing movement. Of course, I am assuming you have one with a display but this can be observed on a mouse type and PC as well. This movement can be caused by several things, such as the satellites are always changing position, signal strength changing and multipath to only name a few. At 4 MPH for a high speed setting, it is quite likely you will trigger a beacon every 61 seconds. The resulting data from the GPS can indicate many angles of change as well. One second, the data may put you north of the last data point and then the next seconds provide data south of either previous position. This is a 180 degree direction change which will certainly trip the angle trip point. Again, it is likely you will get a beacon very often. In a perfect world with a GPS showing exact location all the time this never would happen. For more information: http://gpsinformation.net/multipath.htm If your GPS does WAAS it can be better but it will need to see the geo stationary satellites. This link will describe it a bit: http://gpsinformation.net/waas/acquire-waas-a.html Surveyors have a very accurate system. Maybe it would be worthwhile to investigate the equipment they use. Best regards, Fred
_____ From: [email protected] [mailto:[email protected]] On Behalf Of Chris Sent: Wednesday, July 28, 2010 21:25 To: [email protected] Subject: [tracker2] Smart Beaconing anomaly at 0 MPH possibly caused by turn settings I was experimenting with a low speed Smart Beacon Profile on a T2 (with integrated 5W VHF transceiver) and encountered an unexpectedly high beaconing rate when parked. My settings were as follows: Slow Speed: 0.0 MPH TX rate: 7193 sec High Speed: 4 MPH TX rate: 61 sec Turn angle: 15 deg Max TX rate: 3 sec The shallow turn angle and fast TX rate was set to see if I could reliably double beacon on street corners. The issue arose when parked: Initially, as anticipated, the T2 did not beacon, but after 10 minutes sitting, it began beaconing every few seconds until I shut it off. After thinking about what could cause this it occurred to me that beaconing may be triggered when the uncertainty in sequential GPS readings causes the T2 turning algorithm to be satisfied. However, since I don't know the details of the turning algorithm I can only guess how to avoid this boundary condition. Can anyone shed some light on this?
