Velocity made good, or VMG, is a term used in sailing, especially in yacht racing, indicating the speed of a sailboat towards (or from) the direction of the wind.
At the optimum boat speed and angle to the wind, VMG is maximized, steering closer to the direction of the wind will reduce boat speed, while steering further away from the direction of the wind might give a higher boat speed, but at the cost of a larger deviation in heading, so less progress towards a mark.
Turning up into the wind to a heading of 55 degrees NE causes the boat speed to drop to 4.0 knots.
These data indicate the trade-off between speed and progress toward the upwind mark (to the north in this case).
Finding the heading that moves the boat most quickly towards the mark requires basic trigonometry.
The northward component of the boat's velocity vector is found by multiplying the boat speed (VB) by the cosine of the angle between the true wind direction (north) and the sailboat's heading.
If the course is directly towards a mark, VMC will be identical to speed over ground (SOG).
An ordinary GPS unit will, if it indicates a VMG measurement, of necessity be velocity made good on course.