Under the EUDR, every plot behind a product needs geolocation: latitude and longitude with at least six decimal digits, and a polygon for plots of more than four hectares used for commodities other than cattle (Article 2(28) of Regulation (EU) 2023/1115). A plot whose geometry is wrong cannot be checked for deforestation, cannot be submitted cleanly in a due diligence statement, and weakens the evidence for every product it feeds.
The same problems come up again and again. Here is what they are, why they happen, and how to prevent them.
Why do polygons self-intersect?
A self-intersecting polygon crosses over itself, like a figure eight. It usually happens when:
- the field agent walks the boundary and doubles back;
- points are recorded out of order;
- a GPS jump places one vertex on the wrong side of the plot.
A self-intersecting shape has no reliable area and breaks many geometric checks. Prevention: record the boundary as a continuous walk in one direction, and check validity on the phone before the agent leaves.
Why do polygons fail as unclosed or malformed shapes?
In GeoJSON, a polygon ring must be closed: its first and last positions are identical, and a ring needs at least four positions (RFC 7946). Common faults include:
- rings not closed;
- fewer than three distinct corners;
- duplicated consecutive vertices;
- longitude and latitude swapped, which puts a plot in West Africa into the Indian Ocean, or somewhere else entirely.
GeoJSON coordinates are longitude first, then latitude, in WGS 84. Prevention: export from a tool that writes valid GeoJSON, never re-type coordinates by hand, and validate every file before submission.
Why do plots overlap?
Two plots claiming the same land is one of the most informative failures:
- Neighbouring farmers mapped separately, each drawing a generous boundary.
- The same plot registered twice, by two field agents or under two cooperatives.
- Borrowed plots: a compliant plot declared for produce that really came from elsewhere.
Small overlaps along a shared boundary are often a matter of GPS precision. Large overlaps, or the same plot under two different farmers, are a data-integrity problem and possibly a fraud signal. Prevention: check new plots against existing ones at the time of capture, and resolve overlaps on the ground with both farmers.
Why is a point not enough for large plots?
The EUDR allows a single point only for plots of up to four hectares. A plot above four hectares recorded as a point fails the legal requirement, whatever its accuracy. This happens when:
- the plot’s area was estimated rather than measured;
- a registration campaign captured points for speed, intending to add polygons later;
- several adjoining fields owned by one farmer were recorded as one point.
Prevention: record the area and the geometry together, and require a polygon whenever the declared or measured area exceeds four hectares. Many teams map polygons for all plots so the question never arises.
What is GPS drift and why does it matter?
Phone GPS accuracy varies with the device, satellite visibility, tree cover and how long the device has had a fix. Under a cocoa or coffee canopy, readings can wander. The result:
- boundaries that zigzag;
- vertices scattered away from the real edge;
- polygons that spill into a neighbour’s plot or a nearby forest.
The last case is serious: a boundary that drifts into forest can trigger a deforestation signal on land the farmer never touched. Prevention: wait for a stable fix before recording, record the device’s reported accuracy with each point, walk slowly, and review the shape on a map with the farmer before saving.
Why do declared areas not match the polygon?
The area a farmer declares, the area in a cooperative register and the area of the drawn polygon often disagree. Small differences are normal. Large ones suggest:
- a polygon that covers only part of the plot, or several plots;
- a declared area in a local unit converted incorrectly;
- a plot that has changed since the register was made.
Area also matters beyond geometry. A volume that the declared area could not plausibly produce is a classic sign of produce from undeclared plots. Prevention: compute the area on the phone as the polygon is drawn, show it to the farmer, and flag large mismatches for review.
Why does precision still fail?
The EUDR asks for at least six decimal digits. Data can lose digits when:
- coordinates are copied through spreadsheets that round numbers;
- files are converted between formats;
- points are typed manually from a GPS display.
Prevention: keep coordinates as numbers from device to submission, without manual steps.
Why is fixing at the source better than fixing later?
A polygon error found at headquarters months after collection is expensive to fix. Someone has to find the farmer, return to the plot and map it again, often in the next season. The same error caught on the phone takes a minute to correct, with the farmer standing on their own boundary.
That is why validation belongs at capture:
- Geometry checks on the device: closed, valid, not self-intersecting, enough vertices.
- Area check against the farmer’s declaration, with the four-hectare rule applied automatically.
- Overlap check against plots already registered.
- Accuracy check: GPS accuracy recorded, poor fixes flagged.
- Review with the farmer on a map before saving.
- Offline first: all of this has to work without a network, because most plots are out of coverage.
Then a second layer of checks runs when data syncs: deforestation assessment since the cut-off date, proximity to protected areas and forests, and consistency with purchase volumes.
How does Farmer1st handle plot geometry?
Farmer1st field tools let agents register farmers and map plots offline, with geometry, area and overlap validation on capture. See Field agent management. Our in-house geo service validates polygons from any source, including files you already hold, and runs a multi-source deforestation assessment up to today. See Geo & polygons. Validated plots flow into due diligence reports and statements. See EUDR compliance and the EUDR guide.
Frequently asked questions
Should we map polygons for plots under four hectares too?
The EUDR only requires a point for plots of up to four hectares. Many companies map polygons for all plots anyway: a polygon shows the plot's real extent, makes deforestation checks more reliable and makes overlaps and area mismatches visible. It also avoids re-mapping when a plot grows past four hectares.
Can polygons be corrected after they are captured?
Simple geometric faults, such as an unclosed ring or a duplicated vertex, can be repaired automatically. Faults that change the meaning of the data, such as overlaps between two farmers or a boundary that drifted into a neighbour's field, need someone to check with the farmer. Keep the original and record what was changed, when and why.
What coordinate format does the EUDR Information System use?
Locations can be drawn on a map, entered as coordinates or uploaded as GeoJSON files. The Commission publishes a GeoJSON file description, including solutions to common technical issues, in the help section of the Information System's acceptance environment. The GeoJSON standard itself uses longitude and latitude in WGS 84.
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