The Santo Hoiki (Record of Mountain and Island Bearings) is a record of survey results obtained by Inoh Tadataka and his group, of which 67 volumes are existent today. These volumes were handed down through his family and are currently in the possession of The Inoh Tadataka Museum. The Santo Hoiki is among the 2,345 documents of Inoh Tadataka Related Materials, which have been designated a national treasure. The Santo Hoiki is classified into two types, namely Type A, which consists of 65 volumes, and Type B, which consists of two volumes. Both Type A and Type B record the bearings of mountains and islands. However, the former is a record of bearings of mountains and islands by observation spot, while the latter is a record of bearings by mountain and island. Type A Santo Hoiki contains data from a part of the third survey and all of the fourth through ninth survey records. More specifically, the third survey Santo Hoiki is compiled in one volume, the fourth survey in four volumes, the fifth survey in 14 volumes, the sixth survey in five volumes, the seventh survey in 17 volumes, the eighth survey in 20 volumes, and the ninth survey in four volumes. Each volume contains records of bearings in the order of observation date; therefore, it can be assumed that the records were transcribed directly from field record notes in order to determine the locations of mountains and islands and to correct survey errors. Type B Santo Hoiki was probably compiled from Type A volumes to draw bearing lines on Inoh's map. Research comparing bearing lines in the No. 3 Santo Hoiki to the names of mountains and islands recorded on Inoh's Medium Scale Map (1:216,000) after the fifth survey reveals that the No. 3 Santo Hoiki was compiled in order to draw bearing lines on Inoh's Medium-scale Map.