Radar records map 24 years of global urban height growth

By AI, Created 9:58 AM UTC, May 20, 2026, /AGP/ – Researchers reconstructed annual global built-up height and volume from 1995 to 2018 using calibrated satellite radar data, giving planners a new way to measure how cities grow upward as well as outward. The findings show faster vertical expansion in Asia and the Global South, with implications for energy demand, carbon emissions, and climate planning.

Why it matters: - Cities are changing in three dimensions, not just by spreading across land. - Built-up height and volume affect land-use efficiency, urban heat, air quality, infrastructure demand, energy consumption and carbon emissions. - A long-term global record of vertical urban growth has been hard to build because satellite systems have not always been comparable over time. - The new dataset could improve urban planning, energy-use estimates and carbon-emission assessments.

What happened: - Researchers from China Agricultural University, Tsinghua University, the University of Hong Kong, Curtin University, the University of California, Berkeley, Sun Yat-Sen University and Southwest Jiaotong University published the study in Journal of Remote Sensing on March 4, 2026. - The paper, DOI: 10.34133/remotesensing.1033, reconstructs annual global built-up height and volume from 1995 to 2018. - The team used calibrated radar records from ERS, QSCAT and ASCAT satellite systems. - The study tracks how cities rise vertically worldwide over time.

The details: - The researchers produced annual global built-up height and volume estimates at 5.5-km resolution. - Estimated built-up heights ranged from 0 to 6.5 meters. - The height estimates matched reference datasets with RMSE of 0.32 m and R² of 0.69. - Global built-up volume reached 931.17 km³ in 2018, up from 273.09 km³ in 1995. - That equals an increase of about 2.4 times over the study period. - Asia recorded the fastest rise in built-up volume. - The relative growth rate of built-up volume in the Global South was about double that of the Global North. - The team calibrated radar records into a temporally consistent series. - QSCAT required a second-order regression model because it used a different radar band from ERS and ASCAT. - The calibration raised average temporal consistency across 24 world regions from 0.87 to 0.97. - The researchers combined the radar data with annual impervious-surface information from the GAIA dataset and reference building-height data from 155 cities in Europe, the United States and China. - The model adjusted radar backscatter using impervious-surface area to reduce interference from vegetation and other non-built-up surfaces. - In validation tests, the ISA-adjusted model achieved R² of 0.89 and RMSE of 0.21, beating the non-adjusted version. - Final estimated heights showed RMSE of 1.42 m and MAE of 0.86 m against reference heights. - Cross-product comparisons with global datasets such as GBH and GUH3D showed RMSE values between 0.32 and 0.37 m.

Between the lines: - The study shifts the focus from horizontal sprawl to vertical urban intensity. - That matters because city form can shape density, infrastructure needs and emissions in different ways. - The Global South’s faster growth rate points to a widening role for vertical urbanization outside the highest-income regions. - The work also shows that long-running radar archives can be turned into a consistent urban measurement tool when they are carefully calibrated.

What’s next: - The authors say finer spatial resolution and broader validation data will be needed to improve the dataset. - Future gains will likely depend on better coverage in data-scarce regions. - The team says long-term built-up height datasets could support urban growth modeling, energy-use estimates, carbon-emission studies and urban heat-island assessments. - The findings may also help design cooling strategies as urbanization continues, especially across the Global South.

The bottom line: - The study turns satellite radar into a global yardstick for how cities grow upward, not just outward, over decades.