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In addition, the request for information is also driven by the need to cover data poor regions of low income countries where the coverage of the information is rarely available outside the largest cities (Farrell [15]). In addition, the project recognizes that the EO based information needs to be integrated with statistical demographic and socio-economic records, and generated from new data sources including that of voluntary geographic information and human sensors on the move such as from mobile phones. First, it provides a computing space for image processing specialists to process large data volumes and data streams; second, it provides access of open information products on settlements grouped under specific windows; and, third, it facilitates the dissemination of information and results to potential decision makers. We look forward to future improvements in the extraction of information that will be coming from Big Data Earth Observation (EO) data archives (Corbane et al. [8]) and the incoming open source EO data streams. [Extracted from the article]

The presence of green spaces within city centres has been recognized as a valuable component of the city landscape. Vegetation provides a variety of benefits including energy saving, improved air quality, reduced noise pollution, decreased ambient temperature and psychological restoration. Evidence also shows that the amount of vegetation, known as 'greenness', in densely populated areas, can also be an indicator of the relative wealth of a neighbourhood. The 'grey-green divide', the contrast between built-up areas with a dominant grey colour and green spaces, is taken as a proxy indicator of sustainable management of cities and planning of urban growth. Consistent and continuous assessment of greenness in cities is therefore essential for monitoring progress towards the United Nations Sustainable Development Goal 11. The availability of multi-temporal greenness information from Landsat data archives together with data derived from the city centres database of the Global Human Settlement Layer (GHSL) initiative, offers a unique perspective to quantify and analyse changes in greenness across 10,323 urban centres all around the globe. In this research, we assess differences between greenness within and outside the built-up area for all the urban centres described by the city centres database of the GHSL. We also analyse changes in the amount of green space over time considering changes in the built-up areas in the periods 1990, 2000 and 2014. The results show an overall trend of increased greenness between 1990 and 2014 in most cities. The effect of greening is observed also for most of the 32 world megacities. We conclude that using simple yet effective approaches exploiting open and free global data it is possible to provide quantitative information on the greenness of cities and its changes over time. This information is of direct interest for urban planners and decision-makers to mitigate urban related environmental and social impacts. [ABSTRACT FROM AUTHOR]