This aerial photograph, kindly provided by Robert Smith of the Sherwood Archaeological Society, shows the “crop marks” in the ground, visible at times of dry weather outlined in the crops (which grow differently over buried and otherwise invisible remains of walls/foundations or ditches).
It is possible that this obvious rectangular shape could be the outline of a Roman fort.
The view is looking NNE across the site, which is in the fields between Whinbush Lane (lower left corner), Beanford Lane (top left – the ford is in the trees just off the photo 1/4 of the way across from the left of the top edge) and Oxton Road (across the bottom right corner).
My Oxton 
Hello
The outline is of a Roman marching camp. There is a smaller camp inside it. More details on this camp can be found in the RCHME publication Roman Camps in England, or my book Roman Nottinghamshire, published by Five Leaves. Mark