Table 3.

Features of slums

Domain	Item	Household survey	Ground survey for features of an area	Earth observation	Comment
Built environment	Durability of construction materials	++++	+++	++	Spectral analysis can be used to get some idea of roof materials (especially with ultra-high resolution)
	Layout of lanes and orientation of structures—degree of entropy	++	+++	++++	Earth observation images can be used to quantify this characteristic, for example, using advanced image feature extraction and classification methods such as machine learning
	Density, for example, people sleeping in same room/people per square km	++++	+	+	Clearly, this must be a proxy measurement unless based on household survey
Services	Water	++++	+++ (hard to quantify)	−
	Sanitation	++++	+++	+	Open sewers discernible on very-high-resolution images
	Power	++++	+++	+	Use of night-time light images allow to detect availability of street lighting but the resolution is limited25
	Solid waste management	+++	+++	++++
	Health and education facilities	++++	+++	−
Ecology	Flood plain	−	++	++++
	Probability of subsidence	−	++	++++	Amount of subsidence can be measured accurately from space with radar-based interferometry
	Green and blue space	+	++	++++
Socioeconomic (social exclusion)	Security of tenure/title	+++	+	−
	Level of poverty	++++	++	(++)	The extent to which earth observation images may be a proxy is unknown28
	Crime and safety	++++	−	−
	Social capital	++++	+	−