# Polygon (plot boundary) > A polygon is a closed geometric shape defined by an ordered series of latitude and longitude points that outlines the boundary of a plot of land. Under the EUDR, polygons are required to geolocate plots of more than four hectares used for commodities other than cattle. Also known as: plot polygon, farm boundary, plot boundary, farm polygon ## Why does it matter? A polygon shows the full extent of a [plot of land](/glossary/plot-of-land/). Deforestation checks compare that area with forest maps; a point can only say whether one spot was forest. Polygons also allow area calculation, which supports yield plausibility checks and fraud detection. The [EUDR](/glossary/eudr/) makes polygons mandatory above four hectares (Article 2(28)) and asks the Commission to evaluate that threshold in its 2030 review. ## How does it work in practice? A valid polygon, in the sense of the OGC Simple Features standard, is a closed ring whose first and last points are identical and whose edges do not cross. In [GeoJSON](/glossary/geojson/), polygons use longitude-latitude order in the WGS 84 coordinate system. Quality checks typically include: - closure and minimum number of vertices; - no [self-intersection](/glossary/self-intersection/); - no [overlap](/glossary/overlapping-plots/) with other farmers' plots; - plausible area compared to declared size; - location within the declared country and region; - [GPS accuracy](/glossary/gps-accuracy/) sufficient for the plot size. ## Common pitfalls - Walking only part of the boundary, then closing across the plot. - Recording one polygon for several non-contiguous fields. - GPS drift under dense canopy producing jagged, spiky outlines. - Simplifying geometry so much that the shape no longer matches reality. Farmer1st captures, validates and corrects polygons from field apps, files or imagery through its [geo and polygons](/services/geo-polygons/) service. ## Frequently asked questions ### How many points does a polygon need? The EUDR requires 'sufficient latitude and longitude points to describe the perimeter'. Technically a polygon needs at least three distinct vertices, closed by repeating the first point; real plots usually need many more to follow their shape. ### How is a polygon captured in the field? Most commonly by walking the boundary with a GNSS-enabled phone or device that records points, or by drawing the boundary on high-resolution imagery with the farmer. Each method has different accuracy and cost. ## Sources - [Regulation (EU) 2023/1115 (EUDR), EUR-Lex](https://eur-lex.europa.eu/eli/reg/2023/1115/oj/eng) - [IETF RFC 7946, The GeoJSON Format](https://datatracker.ietf.org/doc/html/rfc7946) - [OGC Simple Feature Access standard](https://www.ogc.org/standards/sfa/)