Doctors measure people’s pulses to determine their health status. Now researchers are proposing to use a similar measure for cities: Using satellite data, they have used artificial intelligence to evaluate in detail how cities are developing around the world. Fluctuations in construction activity served as an indicator for the “urban pulse”. Accordingly, urbanization typically progresses in leaps and bounds, cyclically and asynchronously. The new method could help to better understand the dynamics of urban development and to react more quickly to possible problems.
Cities are more than just a static collection of buildings and streets. As economic and cultural centers and living spaces for people, they themselves are alive. They are subject to constant change due to social, political, technological, economic and ecological influences. In all parts of the world, increasing urbanization brings with it challenges, for example when it comes to social participation, efficient infrastructure and efficient, sustainable use of land.
Living development
“For decades we have only recorded the results of urbanization – a house being built or a road being widened,” says Zhe Zhu of the University of Connecticut. “But you don’t really see the dynamics within an urban area.” In order to make this dynamic and thus the vitality of cities more visible, Zhu and his team propose a new measure: the “Urban Pulse”. “Inspired by the human pulse, in which an electrocardiogram makes invisible activities visible, we use dense satellite time series data to analyze the ‘urban pulse’,” explain the researchers.
Zhu and his colleagues chose construction activity as an indicator of the pulse of cities. “This is a direct indicator of capital investment, labor distribution and material flows – the fundamental drivers of physical growth and economic vitality of cities,” they explain. In addition, the method focuses on the change process itself rather than on its result. “Unlike metrics that measure the end state, such as total impervious surface area or urban land cover, our approach quantifies the speed and rhythm of transformation, thereby capturing the ‘liveliness’ of the urban development process.”
Erratic, cyclical and asynchronous
The researchers evaluated high-resolution satellite images taken between January 2018 and December 2024 for six cities in different parts of the world – Seattle, Shenzhen, Lagos, Mumbai, Dubai and Mexico City. Using artificial intelligence, they derived three typical characteristics of urban development: “First, urbanization is inherently erratic and characterized by episodic events that deviate from baseline trends,” explains the team. The cities analyzed do not expand continuously, but rather go through phases in which large capital investments from politics or business suddenly drive growth.
“Second, urbanization is cyclical and reflects transitions through phases of expansion, stabilization or decline,” the researchers report. However, these phases are difficult to predict and, according to current knowledge, do not follow periodic patterns. The third point the team finds is that urbanization is asynchronous. This means that while one neighborhood is experiencing decline, other parts of the same city may be thriving. “Similar to the human pulse, the urban pulse also varies depending on where it is measured,” write the researchers. “Unlike the human body, there is no single place that forms the ‘heart of a city’ or is representative of the entire urbanization process.” That’s exactly why it’s important to capture the city in its entirety and diversity.
New diagnostic tool
From the researchers’ perspective, the “Urban Pulse” concept can represent a new tool for those responsible in politics, business and urban planning to assess and improve the vitality of a city. “The remote sensing-based diagnostic approach can provide important early warning signals of urban stress and enable targeted interventions to improve urban resilience and sustainability,” the team writes. For example, using satellite data it would be possible to identify early signs of urban decay or unsustainable urban sprawl and take countermeasures in a timely manner.
The ‘Urban Pulse’ can also help people who are new to a city or companies who are considering where to open a branch to better assess the development potential of a city district. “This will be a very powerful tool that influences not only top-down policy decisions by governments, but also bottom-up decisions by ordinary citizens,” Zhu says.
Source: Zhe Zhu (University of Connecticut, USA) et al., Proceedings of the National Academy of Sciences, doi: 10.1073/pnas.2537770123