Field boundary mapper

How the area is worked out

The area is calculated on a sphere rather than a flat plane, using the spherical excess of the ring you draw. A flat calculation drifts further from the truth the further you are from the equator, so a field in Alberta would be measured worse than one in Queensland. This method treats both the same.

How accurate is it?

Accuracy depends almost entirely on how carefully you place the corners and how sharp the imagery is, not on the maths. Satellite imagery is also not current — it may be months or years old, so recent fence moves, new laneways or subdivided blocks will not show.

Not a survey

This is a working estimate for planning, input ordering and rate checks. It is not a surveyed boundary and should not be used to settle a fence line, a lease area, a land transaction or anything else where the legal boundary matters.

Which format to export

For drone spraying, use KML. It has a real polygon type, and it is what DJI Pilot 2 and XAG’s planning workflow import for boundaries. GeoJSON suits QGIS and web mapping. CSV is a plain list of corner coordinates for anything that wants them typed in.

GPX is offered, but it has no polygon type at all — only waypoints, routes and tracks. A boundary exported as GPX becomes a closed track, which is right for a handheld GPS unit and wrong for a drone mission planner. Reach for KML there.

Shapefile is not offered yet. Some DJI Agras boundary and variable-rate workflows expect one, but a shapefile is several binary files in a zip, and we would rather add it once it can be tested against the machine than ship something that only looks right.

Where boundaries are stored

In this browser, and nowhere else. There is no account and nothing is uploaded. Clearing site data, using a private window or moving to another device loses them, so download the GeoJSON for anything you want to keep.