抄録
There are many mountains in Japan, so the phase variation by mountain should be taken into account in Decca chart calculation. A theoretical analysis as a fundamental approach to the problem has been tried. Firstly phase variation by a conical mountain, whose gradient and height are 45 degrees and 10, 000 meters respectively, are calculated. Secondly as a practical example, phase lags by Mt. UOMI, whose height is 214 meters, are calculated and then comparison between calculated values and observation data, which were obtained by Mr. YAMASAKI, Mr. TAGUCHI and Mr. SATO, has been made.
