# Multi-Sensor System for Analysis of Maneuver Performance in Olympic Sailing
## 3 Results  
The data presented in this section are the results of the field test. Figure 3 shows the outlined GNSS path of the entire test in gray, with the section selected for tacking analysis marked in orange. Mean wind direction (MWD) and EOWD are illustrated with red and green direction vectors. Mean values are \(340^{\circ}\) and \(318^{\circ}\). The overall test area spans approximately 1000 \(\times\) 600 m.  
Figure 3: Path of the full field test on the Trondheim Fjord, with selected tacks (orange), full path (gray), direction arrows for measured mean wind direction (red), estimated onboard wind direction (green), and general test area outlined (orange) in the bottom left corner topographical map. A total of 12 tacks were carried out in the selected test section, equally distributed on port and starboard sides. Figure 4 shows all the tacks stacked over each other for comparison, using the apex of the turn estimated by visual inspection as the relative alignment point. Figure 5 shows timeseries data for the six starboard tacks in subplots (a)-(f). The timeseries data for the port tacks are shown in Figure 6. For each figure, the upper plots display the measured rudder angles (blue) and mast angles (green), while the lower plots in each subplot show the velocities and course of the boat. SOG is shown in red and VMG in orange. The average EOWD is illustrated by a flat dotted line (turquoise) through the plots to provide a reference for the changing course angles. Course is plotted in dotted purple. Corresponding performance metrics for each tack are listed in Table 2.  
In Figure 4, we observe that the tacks were performed with consistent entry and exit angles. The variations in entry and exit angles likely correspond to variations in local mean wind and gust conditions, requiring the athlete to adjust course to maintain speed. The overall spread in [entry/exit] course was [21\({}^{\circ}\)/22\({}^{\circ}\)] for the starboard tacks and [18\({}^{\circ}\)/33\({}^{\circ}\)] for the port tacks. The paths plotted in (a) and (b) provide an indication of the distance traveled within the defined time span of the tack. Across all tacks, we observe a gradual course change through the entry of the tack, while the second half of the tack shows more aggressive turn rates. The paths of starboard and port tacks show that the sailor turns slightly more downwind at the exit of the tack, before stabilizing at a slightly higher course, closer to the wind direction. We will now look at a selection of maneuver properties, with different examples from starboard and port tacks. Figure 4: All 12 selected tacks, divided into (**a**) starboard and (**b**) port tacks, relatively aligned with the apex of each tack. In the timeseries of the starboard tacks in Figure 5, we observe a concise rudder movement (blue) at the beginning of each tack. Most of the tacks on starboard show a double low point in rudder angle. In tack 11 (Figure 5f), we observe that the rudder angle has a more gradual change and less presence of double-peaked behavior, with a range of 17\({}^{\circ}\). In the phase after the main direction change, we observe active use of the rudder (\(\pm\)5\({}^{\circ}\)). The mast rotation angles are consistent across all tacks, with stable angles before and after the direction change. The abrupt change in mast angle in the tack can be easily identified in each plot and shows the moment when the boom pivots from one side to the other. The velocity profiles for the starboard tacks provide insights into the overall performance and comparability of the tacks. The mean SOG for the starboard tacks ranges from 2.0 m/s (tack 7 and 9) to 2.4 m/s (tack 1), while the VMG ranges from 1.5 m/s (tack 7 and 11) to 1.8 m/s (tack 1 and 3). Table 2 lists the time from tack initiation until 80% of the entry velocity is reached. For the starboard tacks, the shortest 80%-SOG time is 6.5 s, found in tack 3. We observe that this time is coupled with a mast angle range of 18\({}^{\circ}\) and a rudder angle range of 56\({}^{\circ}\).