Fig. 1From: Simultaneous inversion for source field and mantle electrical conductivity using the variable projection approachDistribution of observatories. The blue triangles show all observatories in the dataset. Note the observatories whose absolute magnetic latitudes are greater than \(56^\circ\) or less than \(5^\circ\) are later excluded from experiments. The red circles mark the observatories used in the experiment from the Discussion sectionBack to article page