def add_dep(dataset):
    if 'LAYER_INTERFACE' in dataset:
        print("LAYER_INTERFACE property alread in DataSet, renaming it to depth...")
    else:
        print("Calculating depth of interfaces...")
        depth = dataset.S1
        depth.values = dataset.DP0.values[:] + dataset.S1.values[:]
        # depth_center =depth_center.assign_attrs({"unit": "m", "long_name": "Depth at Sigma-layer centers"})
        depth = depth.assign_attrs({"unit": "m", "long_name": "Depth at zeta"})
        dataset['dep'] = depth
    return dataset



def makevel(dataset, transpose=True):
    vel = dataset.U1
    angel = dataset.V1
    u = dataset.U1.values
    v =  dataset.V1.values
    vel.values = np.sqrt(u**2+v**2)
    angel.values = np.degrees(np.arctan(u/v))
    vel = vel.assign_attrs({"unit": "m/s", "long_name": "Depth at zeta"})
    angel = angel.assign_attrs({"unit": "°", "long_name": "Depth at zeta"})
    dataset['vel'] = vel
    dataset['angel'] = angel
    return dataset