docs: def exvp(pos_x, pos_y):
      """Convert virtual pixel to real pixel"""
      pos_x = numpy.asarray(pos_x)
      pos_y = numpy.asarray(pos_y)
      # convert virtual pixel to real pixel
      # convert world coordinate to pixel
      center = [1024.5, 1024.5]
      cf  = EMIR_PLATESCALE_RADS
      pos_base_x = pos_x - center[0]
      pos_base_y = pos_y - center[1]
      ra = numpy.hypot(pos_base_x, pos_base_y)
      thet = numpy.arctan2(pos_base_y, pos_base_x)
  
      r  = cf * ra
  
      rr1 = 1 + 14606.7 * r**2 + 1739716115.1 * r**4
  
      nx1 = rr1 * ra * numpy.cos(thet) + center[0]
      ny1 = rr1 * ra * numpy.sin(thet) + center[1]
      return nx1, ny1