Calculate area from a KML file with polygon, parcel and field checks
A KML file can be used for area calculation, but reliability depends on source, polygon closure, CRS and field checks.
Field takeaways
- KML usually carries WGS84 latitude longitude data.
- Area calculation needs a closed polygon.
- Google Earth drawing, parcel reference and RTK survey have different accuracy.
- Area results need method notes.
- MapLab Survey helps compare KML with field records.
What the KML actually holds
A KML stores latitude and longitude on WGS84. Area is not stored in the file; it is computed from the geometry when you open it, which is why two applications can report slightly different values for the same polygon.
Check the shape first
Open the file and look at it before trusting the number. A polygon drawn on a shifted or three-year-old image inherits that error silently.
Projection matters
Computing area directly on latitude and longitude without projecting distorts the result, and the distortion grows with latitude. Use a projected system suited to the region.
Estimate, then verify
A KML area is fine for planning. For anything that enters a contract, the starting point has to be a field measurement.
Try these steps on your own phone.
MapLab Survey handles RTK/GNSS point capture, drawing, area and volume calculations and coordinate conversion, then exports to DXF, KML/KMZ, GeoJSON, Shapefile, GeoPackage, NCZ or CSV. Capture, calculation and export work offline. Live NTRIP corrections and online basemaps need a connection.
Frequently asked questions
Can KML area be calculated?
Yes, if it contains a closed polygon.
Is KML area official?
Not by itself.
Can decare be calculated from KML?
Yes, from square metres.
Can MapLab Survey check KML in the field?
Yes.
Technical references
The field guidance in this article is aligned with the technical and official references below.
Related: Open KML file · Polygon drawing app · Decare calculator · MapLab Survey