Fig. 1From: The Mag.num core field model as a parent for IGRF-13, and the recent evolution of the South Atlantic AnomalyTemporal data coverage of the observatory HMV after data selection in modified Julian days since 2000.0 from 2012-12-31 to 2019-06-27. Additional file 1: Table S1 links the observatory numbers to observatory names and locationsBack to article page