However, using the "shoshaku" measurement used during the period of the Northern and Southern Dynasties (China), it would be 2.94 meters and be nearly equal to the above figure, so there is a question mark over the assertion that they were built after the middle of the seventh century.
しかし、南北朝時代(中国)の小尺（一尺＝24.5cm）でも十二尺（2.94m）とすると殆ど変らない値なので7世紀中頃以降の築造とするには疑問がある。