Evaluating Spatial Interaction Models for Regional Mobility in Sub-Saharan Africa
Fig 3
The actual and predicted amounts of travel from two districts.
The A,D) actual amount of travel, predicted amounts of travel from the B,E) gravity model and C,F) radiation model are shown for two districts. For each map, a continuous density surface was constructed showing the relative spatial distribution of travel. The bar plot shows the amount of travel to all other districts from the district with values displayed in increasing order of distance. Nairobi A,B,C) is the most populated district in the country and includes the capital. In all three figures, the majority of travel (shown in dark blue) is to neighboring locations. The radiation model estimates more travel to the rest of the country than the data or gravity model. Garissa D,E,F) is a rural district bordering Somalia. The majority of actual travel occurs to Nairobi, which the radiation model did not capture. The gravity model was able to predict a large amount of travel to Nairobi, but greatly over predicts travel to the rest of the country.