[GRASS-user] How to plot a vector field?

[david adam]

I would like to plot data which consist of a number of points, each of 
which has a latitude, a longitude, an x-velocity, and a y-velocity.  I 
want to plot an arrow for each point that starts at the proper latitude 
and longitude, and has a length and direction that show the velocity.  I 
used to think of these as vector values, but in GRASS a vector is 
something else.  What is the proper GRASS terminology for this kind of 
data?  What modules do this kind of plot?
tia,
david adam