“三北”协调即将结束
'Three norths' alignment about to end

原始链接: https://www.spatialsource.com.au/three-norths-alignment-about-to-end/

2022年11月,英格兰多塞特郡发生了一次真北、磁北和网格北的罕见一致,被称为“三北”。此一致正在缓慢地向北移动,横跨整个大不列颠。最近来自英国地质调查局和 Ordnance Survey 的数据表明,该一致于2025年12月13日离开英格兰,进入北海。 它将于2026年10月底短暂返回苏格兰德鲁姆,然后在2026年12月中旬再次进入北海,靠近弗雷泽伯勒。这种一致是由地球磁场的变化驱动的(该磁场在2014年显著改变了方向),是一个具有历史意义但转瞬即逝的事件。 专家强调,这种一致对导航没有实际影响,因为使用者仍然必须考虑磁偏角。由于磁场的不可预测性,这种“一生难遇”的现象可能需要几个世纪才会再次发生。

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原文

Dubbed the ‘three norths’ alignment, the correlation began in November 2022 when the true, magnetic and grid norths met in the village of Langton Matravers in Dorset.

But the alignment point hasn’t stood still — it has been moving slowly northwards through Great Britain over the past three years.

New magnetic field data collected by the British Geological Survey (BGS), along with calculations made by Ordnance Survey (OS), indicate that the triple alignment left England at Berwick-upon-Tweed on 13 December 2025 and moved into the North Sea.

“Due to refinement of the underlying models and the prediction data, the alignment’s progress has slowed slightly since the initial predictions back in 2022,” said Mark Greaves, an Earth measurement expert at OS.

“When it crosses the coast at Berwick-upon-Tweed it will have travelled 576 km (about 358 miles) in 1127 days so that’s about 511 m per day (or about 5.9 mm per second or about 0.013 miles per hour).

“It will likely be a very long time before the alignment comes around again.”

The exit at Berwick-upon-Tweed will not be fully the end, though. Predictions indicate that the ‘three norths’ will make landfall again at the end of October 2026 in the village of Drums in Scotland.

Continuing its passage north, the configuration will then leave Scotland at Fraserburgh in mid-December 2026 and head out again into the North Sea, staying in alignment for several years before magnetic north separates off.

Indeed, it is the shifting magnetic field that is the main reason behind the alignment changes.

For instance, as a result of the changing field, in 2014 the magnetic variation in Great Britain was recorded as switching from west to east for the first time since the 1660s.

“The three norths combining in Great Britain has been a once-in-a-lifetime occurrence,” said Dr Ciarán Beggan, Geophysicist at BGS.

“Although part of geospatial history, there is no impact for navigators, pilots and captains once the alignment leaves, and people will still need to continue to take account of the variation between magnetic north from a compass and grid (or true) north on a map.

“It’s been a privilege to be able to observe this phenomenon over the past few years. The magnetic field is not predictable in the long term, so we don’t know how many hundreds of years it will take for this historic alignment to occur again.”

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