puits (1) temps (durée) (1) Afrique du Sud (1) région (1) modélisation (1) modèle (1) information (1) champ (1) méthode (1) navigation (1) Afrique (1) Variation (1) Maps (1) Observations (1) Methods (1) Surveys (1) Observations (1) Maps (1) Variations (1) Time (1) Surveys (1) Prophecies (1) Performance (1) Navigation (1) Models and modelmaking (1) Modeling (1) Maps (1) Geomagnetism (1) Harmonic analysis (1) Example (1)