What is GPS farm mapping?
GPS farm mapping records the location of a farm, and often its boundary, using satellite positioning. The result is geospatial data: a point or a polygon described by latitude and longitude. In agriculture this kind of data feeds geographic information systems (GIS) used for traceability, planning and compliance. For coffee going to the EU it is no longer optional: the EUDR asks for the geolocation of every production plot. Our guide How to map coffee plots with a smartphone explains the method step by step.
Two ways to map a plot
| Plot size | How KahawaTrace maps it | Why |
|---|---|---|
| 4 hectares or less | One GPS point, averaged over about 10 seconds | The EUDR accepts a single point for these plots |
| More than 4 hectares | A boundary polygon, walked on foot with a corner added every 5 metres | The EUDR requires a polygon for plots over 4 hectares |
Agents can also tap points on satellite imagery when walking is not possible, and the app records that the plot was tapped rather than walked.
Accuracy you can see
- A live GPS accuracy indicator, with a target of ±5 metres or better
- Readings averaged and weighted by accuracy, so one bad fix does not spoil a point
- Poor fixes (worse than ±15 metres) are ignored while walking a boundary
- The recorded accuracy is stored with each plot so supervisors can judge it
Smartphone GPS is typically accurate to within 3 to 5 metres in open conditions, but this can fall to 10 to 15 metres under dense canopy or on steep terrain, according to the European Forest Institute. Coffee often grows under shade trees on slopes, which is why averaging and visible accuracy matter.
Checks that run while you map
KahawaTrace checks the geometry before a plot can be submitted and again on the server:
- Boundaries that cross themselves are blocked
- Plots declared over 4 hectares cannot be saved as a single point
- Boundaries smaller than 0.01 hectares are rejected as likely errors
- Overlaps with neighbouring plots and points within 10 metres of another plot are flagged as possible duplicates
- Mapped area that differs from the farmer’s declared area by more than 30 per cent is flagged
- Points outside Kenya are flagged
From the field to GIS and export
Every plot is stored in WGS84, the coordinate system used by GPS and accepted by the EU Information System, rounded to six decimal places. Supervisors see all plots on satellite imagery, colour-coded by status. Approved plots export as GeoJSON, which opens directly in QGIS, ArcGIS and other GIS tools, and can be uploaded with an EUDR due diligence statement. See how it fits together on the EUDR readiness page.
Frequently asked questions
How accurate is mapping with a smartphone?
Typically 3 to 5 metres in the open, worse under heavy shade or on steep slopes. KahawaTrace averages readings, shows live accuracy and stores the accuracy with each plot.
Do field agents need a special app?
No. KahawaTrace runs in the phone’s web browser over HTTPS, which is required for GPS access. Agents sign in with their own account.
Can I use the data in QGIS or ArcGIS?
Yes. Exports are standard GeoJSON in WGS84, which GIS tools open directly.
What if a boundary is wrong?
The supervisor sends it back with a comment and the agent re-maps it. The history of each plot is kept.