Perhaps you have noticed that, when stationary, the location of your GPS tracker seems to move around a bit when GPS Track Manager is logging your waypoints (see example image below). This is a phenomenon known as GPS Drift. Don't worry, this is normal - there's nothing wrong with your tracker.
This behavior is characteristic when the tracker is stationary and occurs particularly in environments where multi-path reception is likely (which is just about anywhere, aside from being in the middle of the desert). In a multi-path environment, the high-sensitivity receiver "sees" more than one signal from a single satellite.
This occurs because the signal is reflected from obstructions such as houses, buildings, walls, vehicles, hills, tree cover, and so forth. The signals arrive at the receiver at slightly different times and, depending on which signal the receiver chooses to believe for any given sample, the distance from the satellite also differs. Multiply this behavior by several satellites, then factor it into the overall position calculation, and the net result is that the receiver perceives abrupt shifts in position. Sometimes these can be significant -- say 40 or 50 feet.
Higher level software in the receiver tries to smooth this out. Generally speaking, it does a better job of this when the tracker is moving. This is because your true change in position per unit time is much larger than the random shifts caused by multi-path reception.
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