DVL Currents
The proof is in the currents
Puma Ocean Racing’s used the Nortek DVL in their victory of the 2011 Transatlantic race. This communicates to us that it is robust and has clear utility. How well this works is best indicated by the estimates of ocean currents. Ocean current estimates along the boat track should be consistent and coherent as the boat changes course (tacks or jibes). It is also interesting to compare the Puma real time current data to independent estimates.
Mar Mostro logged their current estimates during the transit from Lanzarote to Alicante in late September. The data are available here as a Google Earth KMZ file. In order to view it, you first needs to install Google Earth and then open the KMZ file. From here you can view the different data layers by enabling the different data by checking the desired boxes found in “places” to the left.
The image shows the track of Mar Mostro (yellow) as it transits westwards to Alicante. The red lines indicate the real time currents estimated with the DVL. This is overlaid on top of current estimates from a four day average of satellite altimetery data. The data are available for download below on this page.
The KMZ file presents Mar Mostro’s track with current vectors overlaid on top of a current map provided by the Italian Hydrographic Institute (IHI). The estimates are based on satellite altimetry data averaged over a four day period. This means that the IHI current map does not properly represent tidally driven currents or other currents generated on time scales shorter than four days. Note that the current track and the IHI current map have good general agreement; finer evaluation upon zooming in on the image shows that there is indeed current structure that is not well represented in the averaged IHI current map. These differences are currents evolving over time scales not shown in the current map and therefore not available to boats without onboard ocean current measurement methods. It is also clear that knowing current structure in real time can be beneficial when sailing in locations with substantial current gradients (e.g., it would be advantageous to optimize course sailed in order to maximize the time in favorable currents and minimize the time in unfavorable currents).
Download Google Earth KMZ file showing Mar Mostro track and currents
