by ATSupport » Wed Jun 16, 2004 10:56 am
I just checked your geofence settings: your geofence radius was set to
25 feet, which is within the GPS signal fluctuation range. So what happened was the GPS signal fluctuation made your position jump in and out of the fence from time to time, triggering the geoalert, although your phone was physically standing still in one spot.
For your reference, GPS accurary from Garmin (
http://www.garmin.com/aboutGPS/waas.html):
100 meters: Accuracy of the original GPS system, which was subject to accuracy degradation under the government-imposed Selective Availability (SA) program.
15 meters: Typical GPS position accuracy without SA.
3-5 meters: Typical differential GPS (DGPS) position accuracy.
< 3 meters: Typical WAAS position accuracy.
I think the iDEN cell phone GPS is within the range of 2nd level
+-15 meters (+-50 feet).
To conclude, we recommend you set the fence radius no less than 200 feet because of the GPS signal floating.
I just checked your geofence settings: your geofence radius was set to [b]25 feet[/b], which is within the GPS signal fluctuation range. So what happened was the GPS signal fluctuation made your position jump in and out of the fence from time to time, triggering the geoalert, although your phone was physically standing still in one spot.
For your reference, GPS accurary from Garmin ([url=http://www.garmin.com/aboutGPS/waas.html]http://www.garmin.com/aboutGPS/waas.html[/url]):
[quote]
100 meters: Accuracy of the original GPS system, which was subject to accuracy degradation under the government-imposed Selective Availability (SA) program.
15 meters: Typical GPS position accuracy without SA.
3-5 meters: Typical differential GPS (DGPS) position accuracy.
< 3 meters: Typical WAAS position accuracy.
[/quote]
I think the iDEN cell phone GPS is within the range of 2nd level [b]+-15 meters (+-50 feet)[/b].
To conclude, we recommend you set the fence radius no less than 200 feet because of the GPS signal floating.