DIGITIZING CIRCLES?

We are digitizing field boundaries from an aerial photography. A centre pivot
irrigation system had been used on some fields and we need to digitize circles.
Any suggestions on how to digitize circles? I did read in an earlier message
about v.circle. Can somebody tell me where we could locate a copy of v.circle
and how to use it?

Thanks

Anne M. Smith
smitha@abrsle.agr.ca