This is pretty normal behaviour for a modern GNSS receiver and is a result of position “jitter” caused by multi-path signals and scintillation. Traditionally, older GPS systems used to apply a low pass filter (damping) to the calculated positions and this reduced the SOG and COG fluctuations when stationary.

With the GPS160 and its highly accurate Tri-Data technology, we decided to not apply any damping so that the readings were as accurate and with as little lag as possible. The only down side of this approach is this 0.1 Knot indication when stationary, but as soon as you start moving you get the most accurate and lowest latency output.