subroutine invert_RDI(uv,y,nx,ny,nv)
c
c     invert upward looking RDI data along the depth axis.
c
      dimension uv(nx,ny,nv),y(ny)
c
      nswitch = ny/2
      do ibot = 1,nswitch
           itop = ny + 1 - ibot
           yhold = y(itop)
           y(itop) = y(ibot)
           y(ibot) = yhold
      enddo
c
      do iv = 1,nv
           do ix = 1,nx
                do ibot = 1,nswitch
                     itop = ny + 1 - ibot
                     uvhold = uv(ix,itop,iv)
                     uv(ix,itop,iv) = uv(ix,ibot,iv)
                     uv(ix,ibot,iv) = uvhold
                end do
           enddo
      enddo
c
      return
      end