03. Digitising Imagery

  • Reflects physical characteristics of deprived areas
  • May reflect the local context, including social aspects of deprivation, if performed by knowledgeable local experts
  • Delineations are often performed by people without first-hand knowledge of the local context, and thus impose assumptions about what constitutes deprivation locally
  • Types of deprived areas delineated may not be comparable across cities and countries
  • Sharp boundaries delineated around “slums” and informal settlements, especially by outsiders, can have severe consequences for people living in those areas such as eviction, fines, harassment, and stigma
  • Manual delineation of deprived areas is time-intensive and is generally not repeated routinely

Satellite imagery is sometimes used to manually digitize informal settlements. This approach is typically based on a priori definitions of deprivation, for example, defining deprived areas only as informal settlements with high built-up density, irregular layout pattern, small or no internal access roads, small buildings and lack of green spaces. The use of imagery to identify and delineate informal settlements does not depend on predefined areal units and thus may approximate actual informal settlement boundaries; however, the boundaries of more formalized deprived areas may be missed using this approach.

Such delineations may be performed by local or outside experts, and are labor intensive but can provide high-quality, detailed maps required by planners. Manual delineation is sometimes performed to minimum requirements, and if done by several interpreters, might be inconsistent. Furthermore, local experts might disagree in complex settings about the delineation of informal versus formal areas. Although local experts may be from the cities being mapped, delineation of informal settlements is generally performed without involvement of people living in those areas, ignoring local opinions, privacy, and geo-ethics. The degree to which human imagery interpretation reflects local context depends entirely upon who is doing the interpretation and delineation.

More Approaches to Slum Mapping

Current methods of mapping “slum” areas take place in isolation.
IDEAMAPS aims towards integration - using strengths from each approach to build a more detailed system.

01. Field-based Mapping

Field-based mapping is commonly performed by community NGOs such as Slum Dwellers International, and linked to advocacy...

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02. Census & Survey

The widely cited statistic from UN-Habitat – 1 billion slum dwellers globally – is calculated by classifying and counting urban “slum ...

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03. Digitising Imagery

Satellite imagery is sometimes used to manually digitize informal settlements. This approach is typically based on a...

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04. Computer Models

Data scientists use computer models to semi-automatically classify deprived urban areas from satellite imagery and other...

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