Kalman GPS Smoothing Filter

This operator applies a Kalman filter to a position variable to smooth the cruise track.

Echoview accepts a position variable as input.


The Kalman GPS Smoothing Filter Variable Properties dialog box pages include (common) Variable Properties pages and these operator pages:

Operands page

Kalman Smoothing page

This page allows you to enter the settings that will be used to create a smoothed cruise track. The smoothing algorithm only uses good GPS fixes, bad fixes are not considered.

The Smoothing statistics section displays Kalman smoothing statistics.

After changes have been made to the Kalman Smoothing or Data pages, the statistics are displayed as not available ("n/a") until the changes are applied by clicking Apply or OK.



Smoothing slider

Selects degree of smoothing that is applied.

Hint: To view the cruise track that is created from a specific smoothing setting: arrange the cruise track window and Variable Properties dialog box so both windows are visible; move the slider to the required position; then click Apply and observe the changes in the cruise track.


  • A Kalman filter is applied to produce the smoothing effect.
  • The value that you set with the slider has the meaning of 'Expected standard deviation of GPS measurements'. It is a measure of how different you expect a measured GPS fix to be from the estimated (smoothed) one. An estimate is made based upon the history of vessel motion up to that point.
  • If you expect a small difference, then the Kalman filter will put a lot of credibility in the estimate and less in the measurement, resulting in a smoother track. Conversely, if you expect a large difference, you are basically saying that the measurements can vary widely, suggesting less confidence in the estimate and the Kalman filter will rely more on the actual measurements, which has the effect of smoothing less.

Expected standard deviation of GPS error

Shows the standard deviation of GPS error value currently being used by the smoothing algorithm. The value is determined by the position of the slider and cannot be altered in this box.


Processing and smoothing cruise tracks for more details.

See also

About virtual variables
Operator licensing in Echoview