In what follows, this paper illustrates how the capabilities of GIS and satellite imagery can be harnessed to explore and better understand the urban form of several large African cities (Addis Ababa, Nairobi, Kigali, Dar es Salaam, and Dakar). To allow for comparability across very diverse cities, this work looks at the above mentioned cities through the lens of several spatial indicators and relies heavily on data derived from satellite imagery. First, it focuses on understanding the distribution of population across the city, and more specifically how the variations in population density could be linked to transportation. Second, it takes a closer look at the land cover in each city using a semi‐automated texture based land cover classification that identifies neighborhoods that appear more regular or irregularly planned. Lastly, for the higher resolution images, this work studies the changes in the land cover classes as one moves from the city core to the periphery. This work also explored the classification of slightly coarser resolution imagery which allowed analysis of a broader number of cities, 16, provided the lower cost.

# URBAN DENSITY

Urban economists have long argued that a compact and well‐connected city is necessary for the development of an economically strong and livable city. The benefits of dense cities are well documented and empirically proven. Advantages include, among many others, higher firm and worker productivity<sup>10</sup> and improved consumer access to goods and services.<sup>11</sup> In dense cities, firms face stiff competition, thus making only the most efficient and productive likely to survive. When nestled among many other businesses, firms are also encouraged to interact more frequently with their neighbors, promoting a drop in cost and an increase in speed of business transactions.<sup>12</sup> Consumers can also benefit from this density, with the opportunity for shorter commutes, lower travel costs, and more variety of available products.<sup>13</sup> Additional benefits include reduced per capita energy consumption and greater access to running water, sewerage, waste disposal, and public institutions like schools, hospitals and law enforcement.<sup>14</sup> There are several well documented methods to calculating urban density. The first and most common approach is to divide total population living within the city limit by the total area of the city. Figure 1 shows the overall density of the four African cities in this study, and compares them to other major cities in the world.

## **Figure 1 – Overall density of African cities compared to several international cities**

> 10 Melo, Patricia C., Daniel J. Graham, and Robert B. Noland. 2009. A meta‐analysis of estimates of urban agglomeration economies. Regional Science and Urban Economics 39(3):332–342.

> 11 Glaeser, Edward L., Jed Kolko, and Albert Saiz. 2001. Consumer city. Journal of Economic Geography 1(1):27–50.

> 12 Pierre‐Philippe Combes, Gilles Duranton, Laurent Gobillon, Diego Puga, and Sébastien Roux in their article 'The productivity advantages of large cities: Distinguishing agglomeration from firm selection', published in _Econometrica_ 80(6), November 2012: 2543‐2594.

> 13 Couture, Victor. Valuing the Consumption Benefits of Urban Density, Preliminary Draft: 26 November 2012. University of Toronto.

> 14 Larivière, Isabelle and Lafrance, Gaetan. Modelling electricity consumption of cities: effect of urban density. Energy Economics. Volume 21, Issue 1, 1 February 1999, Pages 53–66.

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