I understand that your post are only to me. I choose only to react to your post because your methode has serious drawbacks that can easily create far bigger errors than you think you are making. Also GPS units are far easier to use that two laser beams perfectly aligned on some spot on the shore that is at water level. I appreciate your background but like I said I don't take anybodies background as a garantee that they are right. That includes my own background. I've seen to many high profile characters drop a few balls at different times.

I'm sorry if I come across agressive but I think it is a real pitty that a bunch of people are now of track due to this post. There are talking about laser guns and setting up lasered courses. How is a normal human being going to do that. The laser gun methode is inherently problematic as the shooter needs to be directly in front or behind of the record speeding craft to get the best measurement. How do you align yourself like that without knowing the exact fastest heading. An angle between shooter and heading of only a few degrees will give an error of 0.1 to 0.5 knots ; worse than a GPS track readout.

My point is only that GPS is both the most practical way and pretty accurate (if not to most accurate) if you handle the data right and make sure that deduction or feedback takes out the very much present error.

It is as easily as getting a tracking GPS. set the GPS to storing 1 point per second and start sailing for about an hour trying all headings and than read the track into a PC and determine the fastes 500 mtr track. Windshifts and such do not distrubt the readout as the 500 mtr track can also be a curve with a GPS. WAAAY easier and more practical than setting up a laser course and lasergun and less problematic to implement. And this is using a 150 US$ non-differential (waas) GPS

Sorry Darryl,I respect you but I don't agree with your views even if you are a land surveyer.

Wouter