Force 4 Stripcharts with Unique Options: Compare Measured to Predicted Variables

Using Force 4 Stripcharts to Compared Wind Predictions to Actual Wind
Other tactical programs provide charts ("stripcharts") that track variations in important variables over time. You can use these charts to monitor changes in wind speed and direction, so as to anticipate what changes may lie ahead. Force 4 does this and more, providing Force 4 Stripcharts which track and compare actual to predicted values as you sail. In the example below, the chart simultaneously plots measured wind direction and observed wind direction in the upper portion: the predicted wind from a grib file is the straight red line, immediately below the (jagged line) measured values. (The predicted wind direction is a straight line because the elapsed time shown is only 180 minutes, corresponding to a distance well within the resolution of the grib.)

The lower portion similarly plots observed windspeed against the grib file prediction. In long-distance (ocean) racing, you rely on the grib forecast to calculate optimal routing to the destination. If the grib is not accurate, the routing won't be either. This stripchart enables you to see how well the prediction matches what is actually observed. In this example, wind direction is predicted quite well, but the predicted windspeed is systematically low. You could correct for this effect with the Force 4 Router, which allows you to scale predicted windpeed by a factor to better match observed wind. Or, you could try alternative wind prediction files to see if a different grib is more accurate (Force 4 saves the wind data so you can replot after changing the wind prediction file).
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Other Options with Force 4 Stripcharts

You can open as many Force 4 stripcharts simultaneously as you like. The options include the following:

Current Speed and Direction from Local Knowledge Current Model

Ground Wind Speed and Direction (can be combined with grib file prediction)

Boat Speed and Heading (can be combined with ground speed & heading)

Ground Speed and Heading (COG)   (can be combined with boat speed & heading)

Observed Water Temperature & Predicted Current (use to verify ocean current prediction)

Boat Performance: Compare observed boatspeed to polar performance prediction

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