Map, Journal of the Japan Cartographers Association

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At the beginning of 19^th century Ino Tadataka surveyed almost whole coast lines of Japanese Islands and main roads, and made 214 sheet maps of 1:36000 and 8 sheet maps of 1:216000 in scale. This paper deals with his map compilation and scale-down method. Almost every night, if possible, Ino measured elevation angles of 20 to 30 stars crossing meridian to determine latitude. The Y coordinates of the observation points were calculated from the latitudes using the ratio that one degree difference in latitude was 28.2 ri (or 101.52×36000 sun).Here ri and sun are Japanese old measures. Ino could not measure longitude astronomically because he had not chronometer. He corrected coordinates (x,y) obtained in surface survey “Dosen-Ho”, a kind of open traverse method. The X coordinates of the observation points were estimated as x Y/y. In this way, he obtained coordinates (X,Y) on scale of 1:36000 concerning approximately 1220 astronomical observation points in whole Japanese Islands. For the first step, he prepared local maps of 1:36000 from local surface survey, then corrected them by using the coordinates of astronomical observation points. For second step, he compiled the wide area maps of 1:36000 from local maps to control reference to the coordinates of observation points. The maps of 1: 216000 were compiled from the maps of 1:36000 by using the reduced coordinate values of one six. In this process, the coordinates of the observation points were referred to keep precision of the maps.

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