TWS Error in Version 1.1 and Earlier

FYI for users of 1.1 and earlier, while reviewing the tacking math for version 1.2 I came across an error in TWS calculation when current is involved.  This error results in sub-optimal tacks under low wind and high current conditions. The maximum error is hard to quantify as it depends on wind heading vs. current set and propagates through the polar table, but in my testing I’ve been able to produce a 10% error in speed through the water estimates. The largest error will occur when the wind is directly with or against the current and is most evident with currents over 2 kn and wind Force 3 or less.  Under higher wind conditions, or lower current, the error diminishes.

Course information is still correct, but the error in speed will result in the selection of sub-optimal tacks.  In the testing I did differences between sub-optimal and optimal tacks were on the order of 1-2 degrees. Tack times and total ETA reflect the error in speed.

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