摘要
船磁效应一直是影响海洋地磁测量精度的一个重要因素。传统船磁模型只取磁方位角为变量,改正后测线数据存在系统差和船磁影响的起伏变化,给不断累积的地磁数据拼接带来困难。磁正西北和北东方向的测线网受船的感应磁性变化的影响最小,东西向测线之间船磁影响差异最小,而磁南北向测线之间正好相反,据此可从测线布设方案着手减弱船磁效应影响。完备的船磁模型可以兼顾考虑测线航向、地磁总场、磁倾角和拖缆长度的变化,通过不同拖缆长度的主、副测线网交点差平差或三点各两种不同拖缆长度的方位测量,实现地磁异常分离和完备船磁效应的改正。实例说明固定船磁,甚至负的垂直分量,会使船磁效应随纬度出现可观变化,需要完备船磁模型的解算和改正才能解决这个问题。
Ship magnetism is always an important factor of reducing precision of marine magnetic survey. Since the traditional model of ship magnetism only depends on the magnetic heading, the corrected magnetic data are still possessed of systematic error and up-and-down slope, bringing about difficulties of data fusion for cumulating cruises. Variation of inducing ship magnetism are smallest for the network of geomagnetic northwest and northeast lines, and difference of ship magnetism are smallest between the geomagnetic eastward and westward lines, but largest between the geomagnetic northward and southward lines. Therefore, reducing the influences of ship magnetism needs to take measures at the survey line design. The perfect model of ship magnetism can take all factors into consideration, such as cable length, geomagnetic heading, total intensity, declination and inclination. Cross-over adjustment of main and auxiliary lines with different cable length, or heading survey of two-time different cable length at three different points, will reliably separate magnetic anomaly from ship magnetism, realizing perfect correction of ship magnetism. The example indicates that permanent ship magnetism, especially its negative vertical component, could make the influences of ship magnetism change a lot with latitude, which need to be removed with calculation and correction of the perfect model of ship magnetism.
出处
《海洋测绘》
2008年第3期1-5,共5页
Hydrographic Surveying and Charting
基金
我国近海海洋综合调查与评价专项项目(908-01-DW07
DW08)
国家420专项基金资助项目
关键词
海洋地磁测量
船磁效应
完备船磁模型
测线平差
船磁方位测量
marine magnetic survey
ship magnetism
perfect model of ship magnetism
adjustment of survey network
heading survey of ship magnetism
