# Mapping urban heat islands with satellite data Thermal satellite sensors measure the temperature of roofs, roads, parks and water across a whole city. Mapped over hot days, this land surface temperature shows which districts heat up most, and maps of sealing and green cover help explain why. A city can use the result to decide where shade, trees or unsealed ground should come first. ## How it works Thermal infrared sensors on satellites observe land surface temperature [3]: how hot roofs, asphalt, lawns and water are at the moment of the overpass. Free thermal data come from Landsat 8 and 9. Their thermal bands have a ground sampling distance of 100 m, each satellite repeats its track every 16 days, and the two together every 8 days [1]. Sentinel-3 provides land surface temperature data that can be used to detect urban heat islands [7]. The Copernicus Land Monitoring Service adds hourly estimates from geostationary satellites, which show how heat builds up over a day [4], at a resolution of about 3 km [5]. A heat map shows where it is hot. To see why, it is combined with layers that describe the city's surfaces: the Copernicus imperviousness layer maps sealed ground across Europe at 10 m [8], and the Urban Atlas maps land use and street trees for nearly 800 European cities with more than 50,000 inhabitants [9]. **Figure:** Illustrative map, not real data. Surface heat and green space over the same district, so that hot spots can be compared with green cover. More detail is coming. ESA's Land Surface Temperature Monitoring mission (LSTM) is set to join the Copernicus Sentinel satellites in 2028, with a spatial resolution of 50 m (a sampling distance of about 37 m directly below the satellite) and a revisit of two days with two satellites, and lists urban heat islands among its applications [2] [3]. ## What you get Heat mapping delivers planning inputs, not finished decisions. - **A land surface temperature map** of the whole city for selected hot days or as a summer composite. - **Hotspots by district or block**, ranked and set against sealing and green cover, so that possible causes can be compared. - **Exposure overlays** with population data, to show where vulnerable groups live in the hottest areas. Earth observation can map temperature differences across a city to alert health authorities to risks for specific groups [7]. - **Repeat maps in later summers**, to follow whether new trees or unsealed squares change the surface temperature where they were planned. EUSPA links the growth of urban climate applications to policy attention on heat, including the increasing appointment of municipal heat officers [7]. ## Limits **Limits** - **Clear skies only:** Land surface temperature can be retrieved only under a clear sky. Cloudy periods leave gaps in the record \[4], so a summer map is often built from a few good days. - **One moment per pass:** A satellite in a sun-synchronous orbit passes at the same local time. Landsat 9 crosses the equator at about 10:12 in the morning \[1], so its maps show that moment, not the whole day. Hourly geostationary data fill this gap at a resolution of about 3 km \[5]. - **Air temperature needs other data:** Satellites measure how hot surfaces are, not the air temperature people feel. Air temperature at 2 m comes from stations or urban climate models \[6]. At 100 m, one pixel also covers several buildings and the street between them. ## Related use cases - [Monitoring urban green spaces](https://leto.space/use-cases/urban-green-monitoring/): Where a city is green, and how its trees are doing. - [Tracking land use change](https://leto.space/use-cases/land-use-change/): Where open land has become sealed ground. - [Cities and regions](https://leto.space/cities-and-regions/): All use cases and our consulting for the public sector. ## Find providers and get started Commercial providers turn thermal data into heat maps and microclimate analyses. The [Spacegraph](https://leto.space/spacegraph/) marketplace has a category for urban heat and microclimate. Before you buy, decide which question the map must answer and in what detail. That is the first step of our consulting: we start from your climate goals, check where heat data helps and rank the options. [Strategy and use cases](https://leto.space/consulting/strategy/) ## Frequently asked questions ### Which satellite data is used to map urban heat islands, and how often is it updated? Free thermal data come from Landsat 8 and 9: their thermal bands have a ground sampling distance of 100 m, and the two satellites together pass over the same place every 8 days [1]. Sentinel-3 also provides land surface temperature data [7], and the Copernicus Land Monitoring Service offers hourly estimates from geostationary satellites at a resolution of about 3 km [5]. Each image is usable only where the sky was clear. ### Does a satellite heat map show the temperature residents feel? No. Satellites measure the temperature of the surface itself. What residents feel is the air temperature, which is measured by weather stations or calculated with urban climate models such as UrbClim at 2 m above the ground [6]. Both views belong in a heat plan: the surface map shows where materials store heat, the air temperature shows the exposure of people. ### How do we start a pilot for heat mapping? Start with the decision the map should support, for example where to plant trees first or which squares to unseal, and with the people who will act on it. Then choose the data that matches that decision in detail and timing, and test it on a few districts before the whole city. ## Sources 1. [Landsat 9, U.S. Geological Survey (USGS), accessed 2026-10-06](https://www.usgs.gov/landsat-missions/landsat-9) 2. [LSTM (Copernicus Land Surface Temperature Monitoring mission), European Space Agency (ESA), SentiWiki, accessed 2026-10-06](https://sentiwiki.copernicus.eu/web/lstm) 3. [Copernicus Sentinel Expansion missions, European Space Agency (ESA), accessed 2026-10-06](https://www.esa.int/Applications/Observing_the_Earth/Copernicus/Copernicus_Sentinel_Expansion_missions) 4. [Beyond the heat map: telling the full story of heatwaves with Land Surface Temperature, Copernicus Land Monitoring Service, accessed 2026-10-06](https://land.copernicus.eu/en/feature-articles/beyond-the-heat-map-telling-the-full-story-of-heatwaves-with-land-surface-temperature) 5. [Land Surface Temperature 2018-present (raster 3km), global, hourly, version 3, Copernicus Land Monitoring Service, accessed 2026-10-08](https://land.copernicus.eu/en/products/temperature-and-reflectance/hourly-land-surface-temperature-global-v3-0-3km) 6. [Modelled urban heat island effect for the city of Antwerpen, Belgium, European Environment Agency (EEA), 2024-04-29](https://www.eea.europa.eu/en/analysis/maps-and-charts/modelled-urban-heat-island-effect) 7. [EU Space Market Report 2026, Issue 1: Urban development and cultural heritage, EU Agency for the Space Programme (EUSPA), 2026-05-26](https://www.euspa.europa.eu/sites/default/files/documents/EU_Space_Market_Report_2026.pdf) 8. [Imperviousness Density 2018 (raster 10 m and 100 m), Europe, 3-yearly, Copernicus Land Monitoring Service, accessed 2026-10-06](https://land.copernicus.eu/en/products/high-resolution-layer-imperviousness/imperviousness-density-2018) 9. [Urban Atlas Land Cover/Land Use and Street Tree Layer 2012 and 2018: Product User Manual, Copernicus Land Monitoring Service, accessed 2026-10-06](https://library.land.copernicus.eu/products/Urban_Atlas_Land_Cover-Land_Use_and_Street_Tree_Layer_2012_and_2018_PUM_v6.html) Page: