Fields under water
Click a field. This page takes its outline from the Fields of the World harmonized field data and reads every Sentinel-1 radar image of the year over it. Radar sees through cloud, and calm water mirrors it away: the dark cells are open water. You see when the field flooded, for how long, and the rain that came before.
Zoom in to pick a field
Examples
Fields from the map in a year with a flood. Each picture is the radar image of one day around the field: open water in blue, the field outlined. The stems under it are the water on the field through the year. Click a card to see the field on the map.
About the data
- Fields
- The newest edition of each collection in the Fields of the World harmonized field data, read from its single PMTiles archive. The crop belongs to the year of that edition; in other years the field may have grown something else, or had another outline.
- Radar
- Sentinel-1 radiometric terrain corrected backscatter from Microsoft's Planetary Computer, read while you watch: 10 m cells, a pass every few days from rising and setting orbits (fewer from 2022 to 2024, when only one satellite flew). To keep the download down, at most one image every two days is read, about 1 MB each, spread over the year first and then filled in.
- Water
- A cell counts as open water when its VV backscatter is below −18 dB; the curve shows the share of the field's cells that do. The map shows the same for 2 km around the field.
- Rain
- Daily precipitation from the Open-Meteo historical weather API (ERA5 reanalysis, cells of about 10–25 km): the rain of a grid cell, not of the field. A flood often comes from rain far upstream.
- Caveats
- Wind ruffles water and makes it look like land; water under a crop or among trees scatters the radar back and is missed. Smooth bare soil after rain, tarmac and radar shadow behind slopes can look like water. A single high point is worth a second look on the map.
- Built with
- OpenLayers, ol-pmtiles and geotiff.js; everything is computed in your browser. Code on GitHub.