A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Date: 2017 Aug 8, 12:50 -0700
Your are correct: "IJN" stands for Imperial Japanese Navy. Bowditch (1966 ed., Art. 2110, p. 534) says of him:
In 1920 the New Altitude and Azimuth Talbes by Sinkiti Ogura, Japanese hydrographic engineer, were published in Tokyo... Both the Ogura and Yonemura (art. 2109) tables are given in the same book, the Japanese Hydrographic Office Pub. No. 225. An English edition, with slight modifications in the Ogura method, was published in 1924.
Some further discussion of Ogura's method and its relatives by Charles H. Cotter is on-line at http://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0373463300033932