Greenwich Observatory Monthly Magnetic Data (1841-1925)

1841 to 1925 monthly mean magnetic data from the Greenwich Magnetic Observatory, digitized by the British Geological Survey. The dataset includes standardized inclination and declination values in arcminutes, with some horizontal and vertical force values converted to nanoTeslas. It provides a digital record of historical yearbooks for the magnetic research community.

Use Cases

• Analyzing long-term trends in Earth's magnetic field based on 84 years of monthly mean data.
• Studying historical magnetic declination and inclination changes based on standardized arcminute values.
• Investigating the conversion and consistency of historical force measurements (horizontal/vertical) to nanoTeslas.
• Validating and calibrating modern geomagnetic models using historical benchmark data from a key observatory.

Strengths

• Covers a long historical period from 1841 to 1925, providing 84 years of continuous monthly data.
• Data is standardized, with inclination and declination converted to a common unit (arcminutes).
• Produced by an authoritative organization, the British Geological Survey (BGS).
• Force data from 1912 onward has been successfully converted to the standard unit of nanoTesla.

Limitations

• Conversion of horizontal and vertical force values from 1868 to 1911 to nanoTeslas had limited success due to inconsistent scaling factors.
• Column-level documentation is absent; field semantics must be inferred after download.
• Data may reflect temporal and instrumental bias inherent to historical measurement techniques at a single observatory.

Provenance

Source

British Geological Survey (BGS)

Collection Method

Digitization and standardization of monthly mean data from the Greenwich Magnetic Observatory yearbooks.

Time Range

1841 to 1925

Freshness

Last updated 2026-04-09 08:30:04.706828; freshness should be verified.

Geography

Greenwich Magnetic Observatory (GRW) at 51°29'N 0°0'E