A radar record of the European growing season
SAGRIS is a continuously maintained archive of land use and land cover maps
derived from Sentinel-1 C-band polarimetry SAR. Radar sees
through cloud, so a season can be observed to the end wherever it falls —
which is why the record is unbroken rather than patched around clear days.
This catalogue holds — national archives and
— maps covering —. Every country is
processed the same way every season, so the value of the archive is not any
single map but the comparison down the years: the same
ground, the same method, one season after another.
Each country and year carries two maps, answering two different questions.
They are described next, and confusing them is the commonest way to
misread what you are looking at.
Two tiers: what changed, and how hard it was worked
Land use change — the dynamic map
Three months of radar backscatter combined as one image, one month to each
colour channel. A field takes the colour of the month its signal was
strongest, so the picture is about timing within the season:
when a crop closed its canopy, when it was cut, when bare soil reappeared.
In practice this reads as a crop map. Fields that peak together carry the same
colour, and the crops that dominate a region separate out cleanly. Use it to
ask what was grown here, and when did it happen.
Land cover status — the statistical map
The same season summarised statistically instead: the upper, middle and lower
percentiles of the backscatter distribution, again one to each channel. Nothing
here is about a particular month. The colour describes how the surface
behaved across the whole year — how stable it stayed, how
much it was disturbed.
That makes it a map of human impact and farming intensity. Ground that was
never ploughed looks quite different from ground worked repeatedly, and
permanent vegetation separates from annual cropping. Use it to ask
how heavily was this landscape worked this year.
The two are not alternatives. The change map tells you what the season did;
the status map tells you how much was done to the land. They are most useful
read against each other for the same country and year.
Opening a map
- Find the country. Scroll the list on the left, or type
into the search box — a country name, a three-letter code, a year, or the
words
status and change all narrow it.
- Open the country. Clicking its name unfolds two rows of
years, one for each map type. The range beside the name shows how far back
that country's record goes.
- Pick a year. The map loads and the view moves to that
country. Where a year appears twice, the two cover different parts of the
season and the months are shown on the chip.
One map per country
A country shows one map at a time. Choosing another year, or
the other map type, replaces what was there rather than stacking on top of it.
This is deliberate: two radar composites of the same ground would obscure each
other and neither could be read.
What the year buttons are telling you
- Filled amber — the active map. This is the one the info
panel describes.
- Amber outline, no fill — drawn on the map, but not the
active one. Click it to make it active and the panel switches to it.
- Plain — not currently drawn.
Clicking the active map's own button switches it off and folds that country
away. The panel then hands back to whichever map you had selected before.
Reading across a border
More than one country can be displayed together, so a region that straddles a
border can be read as one landscape instead of two. Open the second country
and pick a year exactly as before; both stay on the map, and the info panel
lists the others under the active one.
Keep the maps comparable. Every country on screen should be
showing the same map type and the same season of
the same year. Nothing prevents you from mixing them, and nothing
on the finished picture will show that you did.
A change map beside a status map puts two unrelated quantities in one frame:
the colours look comparable across the border and mean entirely different
things. Two different seasons do the same at a subtler level — a crop that
peaked in May on one side and one that peaked in July on the other will appear
to differ when they may not. Either combination produces a map that is not
merely uninformative but misleading, and it will mislead
anyone you show it to as well.
Before you screenshot or share a multi-country view, check the panel: the
active map's type and period are at the top, and the others are named beneath
it. Then dim them together with the opacity slider if you want the backdrop
to read through.
The panel on the right
The panel always describes the active map — the one with the
filled year button. Its heading gives the country, the map type and the period
covered, and beneath that the other countries currently drawn.
Opacity
Fades the radar towards the backdrop. When several countries are on it moves
all of them together, so a region stays consistent.
Backdrop
What sits beneath the radar: a dark canvas, a topographic map, or streets.
It shows through as you lower the opacity, and frames the coastline at the
edges of a country's coverage.
Topo map
Places draws settlement names and Roads the
road and railway network, both above the radar — anything the backdrop
carries of its own is underneath it and invisible. Each is only meaningful over
part of the zoom range, so outside that range the button greys out and says so
rather than leaving a layer on that draws nothing.
Layer details and the two Copy buttons
Below the controls: the composite type, the statistic, the sensor,
polarisation, projection, the zoom levels the tiles exist at, and the internal
layer name. Copy tile URL and Copy layer JSON
take the active map into your own tools — see the next topic, because the URL
does not behave the way a web address does.
Getting the panel out of the way
The × in its corner hides it for a clean screenshot; a
Layer info button appears at the top right to bring it back.
The scale bar and the Geomatrix rights statement sit inside the map frame, so
any screenshot carries both.
The tile URL is not a web address
Copy tile URL gives you something of this shape:
https://sagris.landimage.info/tiles/LIT/S1_VV_M01_Q2_AD_2025_RGB654_LIT/{z}/{x}/{y}.png
Those braces are the point. This is an XYZ tile template, not
a page: {z}, {x} and {y} are placeholders
a mapping client fills in with the zoom and grid position of each tile it needs.
Pasted into a browser it resolves to nothing, because no single file lives at
that address — the map is hundreds of thousands of small images and the client
works out which ones to ask for.
Where it does work
- QGIS — Browser panel, right-click XYZ Tiles,
New Connection, paste the template as the URL. It then behaves like
any other raster layer.
- Web mapping libraries — Leaflet's
L.tileLayer(url), OpenLayers' XYZ source,
MapLibre's raster source, and the equivalents elsewhere.
- Desktop and server GIS — anything that accepts a Google or
OSM style XYZ tile cache, including ArcGIS Pro, MapStore and GeoServer.
The tiles are published in the Web Mercator tile scheme
(EPSG:3857) that those clients expect. The underlying products are
produced in EPSG:3035, which is what the panel reports as the
projection; that is the analysis projection, not the tile one.
Copy layer JSON
The same layer as a small block of metadata — title, abstract, bounding box,
zoom range, temporal extent and attribution — for pasting into a map
configuration rather than typing the fields out.
Sending someone exactly what you see
The address in your browser changes as you work. Each map that is on appears in
it, in the order you switched them on:
https://www.sagris.eu/#LIT/change/2025,LAT/change/2025,EST/change/2025
Copy that address and whoever opens it gets the same three countries, the same
map type and the same season, already drawn. It is the most reliable way to
hand over a regional view, because it carries the combination rather than
leaving the other person to rebuild it.
The parts are simply the country code, the map type — change or
status — and the year, so a link can also be written by hand. A
bare country code such as #LIT opens that country's most recent
change map.
Anything unclear, or a country you need that is not here:
info@geomatrix.lt.