Talk:Velocity made good

I think this article has a number of inaccuracies and misleading statements.

Firstly VMG does not measure progress towards a mark (a race course mark or a waypoint)as stated, it measures velocity directly to or from the wind. (VMC measures progress to a mark).

Also, the use of degrees of the compass and headings (compass heading of the boat) are adding unnecessary confusion. The VMG uses angle degrees (as in trigonometry), not degrees of the compass.

To move the article on, consider:

The formula for VMG calculation is VMG=BSP*Cos(TWA) where: VMG is Velocity Made Good. This is either to the wind or away from the wind. It is not to a mark on the chart or to a waypoint. It is a velocity through the water, not a velocity over the ground. BSP is Boat Speed. This is the speed of the boat through the water, not over the ground (SOG) TWA is True Wind Angle. The angle between the true wind direction (TWD) and the fore/aft centreline of the boat. (TWD is the direction of the wind that would be experienced if the boat was not making way through the water, but may be making way subject to any tide or current - It is not the same as Ground Wind, which is the wind that would be experienced if standing on land or anchored)

VMC on the other hand is calculated from the formula:

VMC=SOG*Cos(BRG-COG) where; VMC= Velocity Made on Course. This is the velocity made toward a specified mark or waypoint. SOG= Speed over Ground BRG = Bearing to the mark or waypoint COG = Course over Ground

The big difference between the two is that VMG measures velocity through the water in relation to the wind, whereas VMC measures velocity across the ground in relation to a specified fixed position (a mark or waypoint)Notsailingtoday (talk) 03:31, 13 June 2013 (UTC)


 * I agree that the article is confusing (confused), and while you seem to want to make it better, you make some common editorial mistakes. First you introduce more jargon. Don't use it without defining it (unless an 'average' high-school freshman would be expected to understand the term - ie. no trig & no sailing terminology). Second, you assume that VMG does not apply to ice or sand sailing (both 'over ground'). And MOST importantly, you fail to provide any references.173.189.79.42 (talk) 18:49, 12 May 2015 (UTC)

This article seems to be confusing VMG with VMC. The B&G instruments website has a good document on the topics and can be found here: — Preceding unsigned comment added by 71.179.105.152 (talk) 20:37, 9 July 2016 (UTC)

VMG is covered on page 10. — Preceding unsigned comment added by 71.179.105.152 (talk) 20:39, 9 July 2016 (UTC)


 * This link is dead, but I found it instead at http://busse-yachtshop.de/pdf/bg-triton-2013-bys.pdf . The explanation in this document is pretty perfect, and could serve as inspiration for the text here. -- Egil (talk) 19:00, 26 August 2018 (UTC)

Bold edit
I went ahead and removed the content myself and others could not make sense of, and rewrote a bit. Please review. --- Egil (talk) 16:18, 5 September 2018 (UTC)

True Wind and VMG
VMG is NOT the cosine of the angle between true wind direction and heading, multiplied with boat speed. It's the cosine of the angle between true wind direction and the TRACK THROUGH WATER, multiplied with boat speed (through water). Mind the leeway...

Otherwise, the results will turn out to be too optimistic.

Compare with the B&G leaflet ('moving carpet'): http://www.ockam.com/2013/05/15/true-wind/ (By the way, Ockam's first graph isn't quite correct. Apparent wind has to be computed here with the track through water, not the heading. Leeway, again...)

Bonfire