From space
Official numbers and satellite data, in one place
Nine kinds of satellite data are open: dams from space, greenness, burnt area and fire, drought, surface water, built-up area, land cover and people, air, heat and night light. Each puts what government publishes beside what open satellites measure, with the history of both.
- The official figureFrom the Gazette or the department, as always.
- The view from orbitOpen satellite data, measured by code for the same place.
- On one pageSide by side, with the history of both, and neither one judged.
What we measure
Nine kinds of satellite data are open: dams from space, greenness, burnt area and fire, drought, surface water, built-up area, land cover and people, air, heat and night light. We promise no date for what is still to come.
| Layer | What it shows | Smallest place | How far back | How often | Status |
|---|---|---|---|---|---|
| Dams from space | The water surface of each DWS dam, beside DWS’s weekly level | Each dam (189 of 227 with an outline) | Monthly from January 2017 (Sentinel-2); yearly from 1984 (Landsat) | Monthly | Early access since 13 November 2026 |
| Greenness | How green the land is against its normal for the month | Ward | Monthly from January 2017; normals 1984 to 2020 | Monthly | Early access since 12 November 2026 |
| Burnt area and fire | Where land burnt, and when: fire detections and hectares burnt | Ward | Monthly; detections from 2012 (VIIRS), burnt area from July 2018 | Monthly | Early access since 12 November 2026 |
| Drought | Dry spells against the long normal, joined to dams and rain | Ward | Monthly; a ward from 2015, larger places from 1951 | Monthly | Early access since 12 November 2026 |
| Surface water | Open water seen on the ground, year by year: the permanent part and the part that comes and goes | Ward | Yearly from 1984 (Landsat) | Yearly | Early access since 13 November 2026 |
| Built-up area, land cover and people | Built-up land by ward and year only, the land cover of each ward, and people as a modelled estimate | Ward | Built-up from 1975 (every five years); land cover 2021; people 2015 to 2026 | Yearly | Early access since 12 November 2026 |
| Air | Nitrogen dioxide and sulphur dioxide over each place, modelled by the Copernicus Atmosphere Monitoring Service from satellite readings (Sentinel-5P’s own columns to come) | Municipality | Monthly from 2003 | Yearly | Early access since 13 November 2026 |
| Heat | How hot the ground gets: land surface temperature on clear mornings, each summer and each ward against its municipality | Ward | Monthly from 1984 | Yearly | Early access since 13 November 2026 |
| Night light | Light seen from space at about 1:30 in the morning, by ward, month and year: light, not wealth | Ward | Monthly from January 2012 (NASA Black Marble) | Monthly | Early access since 13 November 2026 |
Also from Copernicus, but modelled rather than seen from space: rainfall and temperature by ward (a European weather model).
What a satellite can and can’t tell you
- Cloud hides the ground. A month with too much cloud over a dam has no reading, and we say so.
- A pixel is 10 to 30 metres across, or much more for some layers. Small and narrow dams are hard to measure.
- Measured from space is not an official reading. A dam’s surface area and its volume are different things.
- Modelled layers are labelled as modelled.
How we treat places where people live
- We report built-up area by ward and by year.
- We do not name or outline settlements.
- We do not publish close-up pictures of homes.
- Night light is shown as light, by ward and year.
Check it yourself
Each release lists the satellite scenes it used, and every picture we made has a fingerprint. How to check a fingerprint.
For researchers
- The API and the fields, with every release and what changed in it (changes).
- The dam outlines and how they were made, free under the ODbL.
- Each dam’s page shows its pictures, its water since 1984 and DWS’s level beside it: start at dam levels.
Credits
- Monthly water and pictures from 2017: Contains modified Copernicus Sentinel data (the years shown on each picture). Sentinel-2 Level-2A from the AWS Registry of Open Data.
- Yearly water from 1984 and a picture a year to 2016: Landsat imagery courtesy of the U.S. Geological Survey; Digital Earth Africa (CC BY 4.0), modified.
- Dam outlines: © OpenStreetMap contributors, ODbL 1.0 (offered free on /open, with the method).
- Dam levels: the Department of Water and Sanitation’s weekly State of Dams report.
- Greenness: NDVI Anomaly and NDVI Climatology, Digital Earth Africa (CC BY 4.0), modified; Landsat imagery courtesy of the U.S. Geological Survey; contains modified Copernicus Sentinel data 2017 to 2026. Second reading: generated using European Union’s Copernicus Land Monitoring Service information (NDVI 300 m), modified.
- Drought: contains modified Copernicus Climate Change Service information (ERA5-Land; ERA5-Drought, DOI 10.24381/9bea5e16), CC BY 4.0; neither the European Commission nor ECMWF is responsible for any use that may be made of it. Greenness in the index: Digital Earth Africa (CC BY 4.0), modified.
- Fire detections: we acknowledge the use of data and/or imagery from NASA’s Fire Information for Resource Management System (FIRMS), part of NASA’s LANCE. Burnt area: generated using European Union’s Copernicus Land Monitoring Service information (Burnt Area 300 m v4, DOI 10.2909/8fa58061-28ab-49bb-9b77-c26b50733e34), modified.
- Surface water: Water Observations from Space, Digital Earth Africa (CC BY 4.0), modified; Landsat imagery courtesy of the U.S. Geological Survey. Cross-check: Source: EC JRC/Google; Pekel et al., Nature 540, 418-422 (2016).
- Air: contains modified Copernicus Atmosphere Monitoring Service information 2003 to 2025 (CAMS global reanalysis EAC4 monthly averaged fields, DOI 10.24381/fd75fff2), CC BY 4.0; neither the European Commission nor ECMWF is responsible for any use that may be made of the Copernicus information or data it contains. Modelled, not ground readings.
- Heat: Landsat imagery courtesy of the U.S. Geological Survey (Landsat Collection 2 surface temperature, through Digital Earth Africa’s copy); clear cells averaged over each place by Unmapped. The ground’s temperature, not the air’s.
- Night light: NASA Black Marble VNP46A3 and VNP46A4, collection 2, NASA LAADS DAAC (doi:10.5067/VIIRS/VNP46A3.002, doi:10.5067/VIIRS/VNP46A4.002); summed over each place by Unmapped. Light seen from space at about 1:30 am, not wealth.
- Land cover: ESA WorldCover 2021 (CC BY 4.0), modified. Built-up area: GHSL, European Commission Joint Research Centre (CC BY 4.0), modified. People: WorldPop (www.worldpop.org), CC BY 4.0, modified; a modelled estimate, not the census.