Memoirs of the Kakioka Magnetic Observatory Supplement No.05， p.185, March, 1975
Base-Line Value Stability of Geomagnetic Variometer
Base-line value changes of KM-type H-variometers used at three observatories, Kakioka, Memambetsu and Kanoya, for the 1960's are analysed.
Their stabilities are good and the change in each variometer is expressed by a single function of time and temperature for a long time. In practical use of the relation，calculated values are as accurate as the absolute measurement by good magnetometers.
A new term of out-of-phase change is found in the relation for annual temperature variation. Though it is small in general，the term should be taken into consideration for precise determination of base-line values with accuracies better than 1γ.