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在绝对偏角仪测磁偏角D的过程中,需借助于一个已知地理方位角的标志,简称标志,根据标志在仪器上的读数,找出地理子午线的位置,磁子午面与地理子午面之间的夹角即为磁偏角(D)。方位标志设置的稳固程度如何,将会直接影响所测磁偏角的可靠性。本文对拉萨地磁台1957年用水泥墩设置的(D)标志进行了考察,该标志墩面离地平约1.5m,埋深约1m。考察结果发现此标志读数存在近似V型的季节性变化。为了弄清造成这种变化的原因,对1984年在绝对观测室4号墩放置的舒米特仪测得的(D)标志资料与水文站测得的拉萨河水位资料
In absolute declination magnetic declination D process, with the help of a known geographical azimuth signs, referred to as signs, according to the mark on the instrument readings to find the location of geographical meridian, magnetic meridian and geographical meridian The angle between the faces is the declination (D). The degree of solidity of the bearing setting will directly affect the reliability of the measured magnetic declination. In this paper, the (D) signs set by cement piers of Lhasa Geomagnetic Observatory in 1957 were investigated. The pier surface is about 1.5m above the ground and has a buried depth of about 1m. The study found that there was a seasonal V-shaped change in the sign readings. In order to find out the reasons for this change, the (D) mark data measured by Schmidt instrument placed at Pier 4 in the absolute observation room in 1984 and the Lhasa River water level data measured by the hydrological station