What is the Geostrophic wind scale
 

Could someone please explain. There is one in the upper left hand corner on the North Atlantic weather forecast charts at http://weather.noaa.gov/fax/otherfax.shtml

Synoptic charts usually display a geostrophic wind scale so that the wind strength can be calculated by measuring the distance between the isobars at right angles to those isobars, and taking into account the latitude.

Speeds of fronts can also be calculated using this scale, with cold fronts travelling at the full speed of the wind and warm fronts travelling at 2/3 the speed of the wind. Note that the scale does not start at zero when you are using it.