[SEM18-P01] Analyzing the early 19th cenytury's geomagnetic declination in Japan from Tadataka Inoh's Santou-Houi-Ki the 13th roeport.
Keywords:geomagnetic declination , Tadataka Inoh, Santou-Houi-Ki, reference point , target point, interdiciplinary
(1)Interdisciplinary simultaneous analysis: We can increase precise evidence to verify the real azimuth, geomagnetic declination and the reference point where magnetic compass survey was executed, or survey target points recorded in the Santou-Houi-Ki, than traditional way of study separated in each field.
(2) Procedure of analysis: Use the recreation software of scenery and digital map of GSI Japan Chiriin Chizu to know the latitude and longitude accuracy sec of particular survey target points, and the outline position of survey reference point to grasp the outline of each real azimuth from the survey reference point to survey target points. Geomagnetic declination=Real azimuth-Magnetic compass survey azimuth recorded in the Santou-Houi-Ki. Calculate backward the precise position of the survey reference point should be adjusted to the position in accuracy 0.001sec.in latitude and longitude, where all of geomagnetic declination unit of 0.01sec. Calculate from the magnetic compass survey azimuth to each different targets at the reference point are approximately equal to each other. Calculate the average value of each declination unit of 0.001sec.and express it as the geomagnetic declination unit of 1min.on the day and point Tadataka Inoh's magnetic compass survey was executed. To use the consecutive formula of Excell for speed up and Keep accuracy. If it possible to go to the field of the survey reference point, confirm the real scenery and the longitude and latitude by GPS transmitter and recalculate the value of geomagnetic declination.
(3) The outline of isogonic line in Japan archipelago and the distribution of the declination in every 15 min in western Japan coast in those days. begin to appear. Compare the isogonic line of declination in those year's Japanese archipelago by analysis of The Santou-Houi-Ki,with the Historical
Magnetic Declination map by NOAA(1800,1805,1810,1815)is the NOAA's pace of variation West is almost 5 years later than the analysis of the Santou-Houi-Ki in western Japan. (4)However, from the analysis of Santou-Houi-Ki, we can recognise the magnetic declination supposed as the local geomagnetic declination anomaly in southern coast of eastern Hokkaido, some part of Noto Peninsula, Mt. Asama in Ise, Nobeoka city in Kyushu Island etc. and revealed the long western coast of Tsushima island etc.,impossible to drew in Historical Declination Viewer by NOAA. The analysis is developed from the coast area of Japanese archipelago to the inland area of Honshu island. (5)It is able to restore the precise position of survey reference points where Tadataka Inoh's magnetic compass survey was executed the accuracy of less than sec in latitude and longitude ,valuable in local history. It is so accurate as impossible to achieve by other way of study.(6)It is able to change Japan as the concentrated area of data in early 19th century from insufficient area of data and supply data to north east Asia.
Total number of analyzed points exceeded 229. (7)We started the discussion to compile those analysis to the database available to Archeomagnetiism Data base, or NOAA’s Historical Declination Viewer.In this year I will focus on between Niigata prefecture including Sadogashima island from Ishikawa prefecture.