The Bench

10/27/2008

Calibrating with DeWiggler

Filed under:

Software

— Dan @ 9:52 am on

I realize I have been remiss in not discussing our newest software product here: DeWiggler! "What is DeWiggler?", you ask. It’s just about the biggest break-through ever in automated calibration! It removes the tack-to-tack difference, or "wiggle", in calculated wind direction. It does this by providing very accurate calibration values for the parameters upon which wind direction is dependent.

Calibration has traditionally been done manually, with a human noting and calculating the numbers. This takes a bit of artistry to determine what is good data and what is bad data. Sometimes it’s obvious, like when there is too much or too little wind or the waves are too high. Other times, it’s a bit more difficult, like when there is a lot of wind shear throwing off the tack-to-tack wind angles. Most people can do the boatspeed and compass calibration reasonably well, but sometimes the wind calibrations take more than one try to get a good value. This of course can make life difficult, because getting everyone’s schedule together to go out for a calibration run can be pretty impossible. Add the variable weather conditions to this problem, and a racing program might not find the time to do all the calibrations. And it’s nigh impossible to calibrate during races, because everyone is focused on other duties.

Older methods of automated calibration were not much better. They still had the scheduling problems of manual calibration, and they relied on a person to initiate and end the calibration run - this required that the person operating it knew when to begin and end (it’s not always obvious).

DeWiggler solves a lot of these problems. While running, it guides the user through the process rather than relying on the user to guide the program. It tells the helmsman what course to steer, how much distance is left on the leg, and how long to stay on a tack when sailing. Best of all, it can remain running during a race to collect data, so that there are as many data points as possible for the largest sample size!

There are two main parts to DeWiggler: the boatspeed & compass calibration, and the wind calibration. The first part is best accomplished under motor, as it requires that the boat is steered to specific courses over a specific distance. It checks the direct boatspeed and compass readings against GPS data, subtracts the effect of current, and produces a compass offset and boatspeed calibration correction. On the T1 processor, a file can simply be copied to the CF card for the complete compass offset correction.

The second part calculates the wind calibrations. The best part of this is that if the program is left running during a race, it will monitor the wind readings for the entire race, throw out the bad data (like that collected during the pre-start), and produce calibration values from that data. This even allows enough data to be collected to compute a good upwash slope value - something that is typically pretty hard to do manually! It also can analyze tacking performance.

When calibrations were done manually, it was considered a good calibration if the wind direction solution only had a tack-to-tack error of less than 5 degrees, with 3 degrees or less being ideal. For those boats that have completed the DeWiggler calibration, tack-to-tack errors have been consistently less than 1 degree on the first try! This was considered a very difficult proposition when calibrating manually, but it has become the expected norm with DeWiggler.

DeWiggler also can assist with setting the correct calibrations. It can determine the current calibration values set in the system, determine if the screw settings are correct (and if they match the current settings), and then guide the user to set the screw values to the newly calculated values. It really makes the calibration process as painless as possible.

The program is free to download, install, and run. The user is charged only when an analysis of the data is done. The analysis can be purchase through our web store, a servicing dealer, or direct from Ockam. Please see our DeWiggler web page (also linked from the main Ockam page) for more information.