Mapping plots with a GPS phone app for the EUDR

A phone in someone's pocket is how most smallholder plots get mapped. It works, but the way the boundary is walked decides whether the file passes.

Settings that matter

• Coordinates in WGS 84, decimal degrees. Phones report positions in WGS 84, which is what the Information System requires (GeoJSON File Description, Introduction). Some apps can display or export in UTM; choose degrees.
• Six decimals or more. The regulation defines geolocation with at least six decimal digits (Regulation (EU) 2023/1115, Art. 2(28)). Check the export setting: some apps round.
• An export format we can read. GeoJSON, KML, KMZ, GPX or CSV all work.

Walking the boundary

• Area mode, not track mode. A recorded track is a line; lines are not accepted as production places (GeoJSON File Description, Definitions). If the app only records tracks, walk back to the start: when converting, we close a path that ends within 20 m of where it began, and say so.
• Pause at the corners. Standing still for a few seconds lets the phone settle its position. Accuracy is typically a few metres in the open and noticeably worse under tree canopy, which is where cocoa, coffee and rubber grow.
• Do not double back. Walking to a corner post and back the same way makes a spike the system rejects as a fold.
• Keep going the same way round. Stopping to add a missed corner at the end joins it to the wrong neighbour and makes a figure eight.

Fewer points is fine

Apps that record a point every second produce thousands of vertices on a boundary four corners would describe. The Commission recommends fewer points along straight edges to keep files small (GeoJSON File Description, Common errors 16), and the checker's simplification can do it for you within a strict area tolerance. Near-duplicate points, a common side-effect of standing still, are removed safely.