Fig. 2From: Bootstrapping Swarm and observatory data to generate candidates for the DGRF and IGRF-13a, d Spatial distributions of the observatories. b, e Number of observatory data per month (see time windows in the main text). c, f Number of data per observatory (x-axis numbers correspond to the IAGA code given in Additional file 1: Table S1). Upper panel: observatories for DGRF parent model. Lower panel: observatories for IGRF parent modelBack to article page