This study aimed to seek the place names of the areas that were transcribed as islands located in the Indian Ocean at the 『Gangrido』 and understand the arrangement context. To serch for the place names, this study investigated Chinese historical materials and travel records of diverse cultural zones and intended to interpret them according to the capital names of corresponding areas. As a result, it seemed that Nobal(奴發) and Seohyol(西穴) were originated from the names of the Nabhanis and the Scier of South Arabia. It was assumed that Ari(阿里) was from the transliteration of Ali and in particular, it was from the Sanaa under the influence of the Shia Ismaili among Yemen powers. Accordingly, Marongsa(麻龍沙), Noam(奴啱), Mahaphapsuk(馬合哈叔) and Happala(合八牙) as the names of the islands could be interpreted as Malindi, Nubia, Cairo and Alexandria. Cairo was as the capital of the Fatimids who belonged to the Shia Ismaili Family, controlled the business networks connected to the Mediterranean Sea through the Red Sea from the 10th century to the 12th century. Therefore, it was assumed that the places named islands were parts of the continent and arrangement of the pieces, the South India, the southern end of the Arabian Peninsula, the east coast of Kenya, Cairo and Alexandria of the Africa was understood as the merchant networks that actively worked at the Colas and the Fatimids.
For one thing, the part of the continent was named as islands as geographical knowledge was accumulated through sailing. The cases that inland and peninsula were misunderstood as islands were shown both in Islamic and Chinese data in the 12th and 13th centuries. In comparison with the world map of Idrisi, the Gangrido presented more specific and exact and newer information on South India and Bengal Sea. The characteristic was inherited to the 『Zenghe Chart(鄭和航海圖)』. It indicates that the two charts were from the same family. For acknowledging the existence of the Indian Sea Chart before the 『Zenghe Chart』, the trace could be found in the pieces of continent in the 『Ganglido』. The other focus was given on the fact that the continent pieces were influenced by Monsoon season. It was assumed that the geographical concept in respect Monsoon season was inherited from geographical recognition of Persian people in considering of etymology of ‘land above wind’ and ‘land below wind’. Accordingly, it is considered that geographical information on maritime affairs was originated from geographical recognition of Persia and that the pieces of continent were based on that Monsoon what was the most important factor to make the world of the Indian Ocean organized as trade network. At that time, South India, Arab and East African Coast worked as an important bridge to connect and a gate to the world. That is, it is concluded that the pieces of continent in respect to maritime affairs reflected trade networks formed as sailing routines and independent sailing navigation of merchants who worked at the Red Sea and the Indian Ocean.