Classical Slepian functions (Simons et al. 2006) and altitude-cognizant Slepian functions (Plattner & Simons 2017) constructed for region R = Africa. (a) Best-concentrated and (b) second-best-concentrated classical Slepian function for L_tap = 4. (c) Best-concentrated and (d) 60th-best-concentrated classical Slepian function for L_tap = 40. (e) Best-suited and (f) 60th-best-suited altitude-cognizant Slepian function for L_max = 40, r_p = 6371 km and r_s = 6671 km.