Fig. 2From: A harmonic spline magnetic main field model for Southern Africa combining ground and satellite data to describe the evolution of the South Atlantic Anomaly in this region between 2005 and 2010Data centres for model input data. The data bins (\(0.2^\circ \times 0.2^\circ\)) used for satellite input data (represented by square shapes), the middle of each data bin represents a data centre (small dots). The input data are the averages of recorded values within 1Â day in the same bin at different altitudes between 300 and 380Â km. The big black dots are geomagnetic repeat stations. The two red big dots are locations at the ground level used in the evaluation of the new SACFM-2 model. The four groups of green dots are the selected points for independent data at satellite altitude (G1, G2, G3 and G4) used in the evaluation of the SACFM-2 model. The four blue triangles are the permanent observatories HER, HBK, TSU and KMHBack to article page