This is map comes from the 1834 atlas "Cheonggu-do" (靑邱圖), made by Korean geographer Kim Jong-ho (金正浩). The map shows the eastern half of Ulleungdo. Just off the east shore is a neighboring island labeled "Usan" (于山), which was the old name for Ulleungdo's neighboring island of Jukdo (竹島).
Each map page in the atlas has a ruler along the top, side, and bottom. Each segment of the ruler represents 10 ri, which was about 4 kilometers. There are seven segments along the top of the page and ten segments along the side. Therefore Ulleungdo's neighboring island of "Usan" is shown to be about 10 ri (4 km) offshore. Today, Ulleungdo's neighboring island of Jukdo is between 2 and 4 kilometers off Ulleungdo's east shore, depending from where on the east shore you measure.
The Korean government claims that Usando (于山島 - 우산도) was the old Korean name for Liancourt Rocks (Dokdo), but this map and many others show that it was the old name for Ulleungdo's neighboring island of Jukdo, 2 kilometers off Ullleungdo's east shore.