Enable and test static hold on rover gps module

[bitmorse]

"Static Hold Mode allows the navigation algorithms to decrease the noise in the position output when the velocity is below a pre-defined 'Static Hold Threshold'. This reduces the position wander caused by environmental factors such as multi-path and improves position accuracy especially in stationary applications. By default, static hold mode is disabled.
If the speed drops below the defined 'Static Hold Threshold, the Static Hold Mode will be activated. Once Static Hold Mode has been entered, the position output is kept static and the velocity is set to zero until there is evidence of movement again. Such evidence can be velocity, acceleration, changes of the valid flag (e.g. position accuracy estimate exceeding the Position Accuracy Mask, see also section Navigation Output Filters), position displacement, etc.
The UBX-CFG-NAV5 message additionally allows for configuration of distance threshold (field staticHoldMaxDist). If the estimated position is farther away from the static hold position than this threshold, static mode will be quit."