diffpos 1 diffpos compare the contents of two &x3d; files diffpos  .3d file .3d file threshold Diffpos reports stations which are in one file but not the other, and also stations which have moved by more than a specified threshold distance in X, Y, or Z. The threshold distance is given in metres and defaults to 0.01m if not specified. For backward compatibility diffpos will also read the &pos; files produced by earlier versions of cavern, or by 3dtopos.