Definition of "isogonal" []

• Describing lines connecting points on the earth's surface whose magnetic declination is identical. (adjective)
• Having equal angles. (adjective)

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• "Yet Cornelius Schouten, on Easter Sunday, 1616, appears to have found the declination null somewhere to the southeast of Nukahiva, in 15 degrees south lat. and 132 degrees west long., and consequently in the middle of the present closed isogonal system."