VMC Predictor

After couple of years practically unchanged, I have recently made some changes to the functionality of my sollog site. The predictor so far has had two functions, COG and TWA which reflect the two steering modes Sailonline has, continue same course or continue same wind angle. Now there is a third function, VMC - Velocity Made Course.

About VMC itself, there are explanations in SOL-related blogs by the legendary 76Trombones and more recently in the solfans blog. In the predictor view it means that you can set the VMC direction in the degrees-box (or leave it empty for VMC to the next mark). Predictor view will then calculate your course using the best VMC to the given direction (or position in the case of mark).

Technically I have chosen the course to be straight (COG steering) between the reported intervals, i.e. for 6 hour predictor the course is calculated to be 15 minutes COG to the best VMC at the starting point, then a new best VMC course is calculated and next 15 minutes will be to that direction and so on. For longer predictors the straight parts are naturally longer.

Other possibility would be to calculate best VMC for each calculation the predictor does but initially I have thought this is a better compromise for possibly using the result for setting DC's (delayed commands) and judging tacks, gybes or polar hops. The VMC predictor can be thought as a "poor mans router". If you have ideas how it could be improved I am interested to hear them as I am not sure if the current implementation is the best possible.

The other change to the site is not about adding functionality but choosing to restrict some features only for boats which are SYC members. As the site doesn't require any login there is no way to know who the user is. However, boats which are not SYC members can't be used as reference boats in the real time statistics and neither is the predictor view available for non-members.

To clarify this change is completely my own idea to encourage people to join SYC and it has nothing to do with SOL management. I personally don't get any money from the SYC membership fees.