code: def displaceAbs(x, y, sourcePos_x, sourcePos_y):
      
      x_mapped = x - sourcePos_x
      y_mapped = y - sourcePos_y
      absmapped = np.sqrt(x_mapped**2+y_mapped**2)
      return absmapped
docs: calculates a grid of distances to the observer in angel
  
      :param mapped_cartcoord: mapped cartesian coordinates
      :type mapped_cartcoord: numpy array (n,2)
      :param sourcePos: source position
      :type sourcePos: numpy vector [x0,y0]
      :returns:  array of displacement
      :raises: AttributeError, KeyError