Step 1b: Select a Top-Down and/or Bottoms-Up mapping approach

There are two main approaches to begin geographically mapping network infrastructure and access, depending on the geographic scope of the exercise. The first is top-down and involves mapping a large geographic area by accessing secondary data sources and identifying gaps in infrastructure service. This differs from the more granular and localized bottom-up approach, which starts with an ex-ante selection of a specific locality and builds an understanding of current conditions through a direct census of residences and physical survey of network assets. Both approaches overlay infrastructure assets and coverage against population density. The figure below differentiates between the two, but a given mapping exercise may take elements from both approaches, accessing secondary mapping of network assets, population density and other relevant infrastructure, and combining it with an on-the-ground survey and census.

Figure 13: Differentiating between two different approaches to mapping unconnected and underserved populations

Top-down approach:

Large geographic areas (national or sub-national) are mapped by accessing secondary mapping data in order to identify infrastructure coverage gaps. Additional characteristics:

  • Data gathered from secondary sources such as national government agencies or third-party aggregators (e.g. satellite data, operator infrastructure, etc.)
  • Tends to cover large geographic areas
  • May develop a multipronged approach to connectivity interventions beyond a single site/location

Bottom-up approach:

Starts with the specific, targeted locality, mapping local data and testing for different aspects of network infrastructure availability. Additional characteristics:

  • Local mapping (testing network infrastructure available in the vicinity)
  • Adding socio-demographic attributes at the local level collected via census
  • Includes relevant geographic and environmental conditions