Monitoring Global Urban Expansion Phase II Pilot Program Infographic
Identifying Expansion Areas of Cities
In each city, we have an outline of the expansion from 1990 – 2000, and from 2000 – 2010. As an example, this is the 1990 – 2000 expansion of Addis Ababa. This work was carried out by University of Connecticut.
Identify Random Set of Ten Hectare Locales
Within this expansion area, we set out to sample smaller areas encompassing several blocks, which we term locales. Each locale encompasses approximately 10 hectares – an area that is neither too small to be statistically significant, nor so large as to be difficult to analyze. The location of these locales relies on a random distribution generated by a Halton Sequence.
Digitization of Locales
The analysis of the imagery takes place within each circle. Our fundamental unit of analysis is the locale, which generally consists of blocks bordered by streets. Therefore, the first step is to convert the 10 hectare circle into a polygon, bordered by streets, that roughly approximates the original area. This is the locale.
Identify Locale Boundaries
The line of the locale runs through the median of the street, allowing us to calculate the width of the street by doubling the distance from the edge of the block to the local boundary.
Identify Blocks and Roads within Locale
After tracing the locale boundary, the next task is to trace the boundary of every block, snapped tightly to its edge. The land is categorized by its use – either open space, non-residential land, or one of four types of residential land.
The six land use categories we’re using are Open Space, non-residential, atomized, informal planned, formal planned, and housing project developments.