Loxodromes (rhumb lines) are plotted as straight lines on maps in Mercator projection. The angle the loxodrome makes with the meridian, i.e. bearing or azimuth, has been called “dakaku” in the field of cartography and geography in Japan. “Dakaku”, if translated literally, is the steering angle or helm and the same word is used in the field of navigation in this meaning. Therefore, this wording is confusing and not appropriate.
This word has been used more than ninety years in cartographic literature in Japan. The author, however, argues that we should cease using this word as meaning bearings of loxodromes and just use “houi” which means bearing instead.
It is unknown why this wording “dakaku” occurred, but the author conjectures that the word “houi” has been solely used as meaning the direction from point A to point B in cartography and geography in Japan and that has prohibited the use of the word “houi” for the direction of loxodrome. But this is not proper usage of Japanese language. “Houi” can be used in this meaning of course but is also used at one point on the Earth to express bearings. There is no problem to use “houi” as meaning bearings of loxodromes.
Therefore, we should cease using “houi” in a very limited sense but freely use this word in the meanings of original Japanese language also in the field of cartography and geography
