First isogonic chart (Halley's magnetic variation chart)
Primer mapa de isógonas (carta de variación magnética de Halley)
- Date
- 1701 · confidence high
- Place
- London, England, United Kingdom
- Credited to
- Edmond Halley
- Field
- Cosmos & Earth
What was discovered
After two voyages in the Paramore (1698-1700), Halley published a chart of the Atlantic with lines joining points of equal magnetic declination. It is the first thematic map with isolines and helped correct the compass at sea.
Halley also proposed concentric magnetic shells rotating at different rates inside the Earth, a hypothesis since rejected.
What it led to
- thematic maps with isolines (isotherms, isobars)
- models of the Earth's magnetic field
- improved navigation with variation corrections