Preparing KML for cadastre: showing a parcel correctly in Google Earth
KML is a practical way to show a parcel to a client or field team. But it is a visual exchange format; without correct transformation the parcel can shift and be misread.
Field takeaways
- KML uses WGS84 geographic coordinates, not projected metre coordinates.
- Coordinate order is longitude, latitude, altitude.
- A polygon ring must be closed: first and last coordinates match.
- Google Earth imagery is visual context, not a legal cadastral base.
- Official work follows authorised data and required institutional formats.
The job KML does well
KML is excellent at showing quickly where a parcel is. An owner, a site manager or a field crew sees the boundary in Google Earth; the road approach, the surrounding development, the stream bed and the neighbouring parcels explain themselves. Treating the KML as an official coordinate delivery, however, is a mistake — it is the visual layer of the job, not the legal one.
The biggest error: metres written straight into KML
KML writes coordinates in degrees, in the order longitude, latitude, altitude. Metre-based coordinates such as TM or UTM must be transformed to WGS84 geographic coordinates first. Swapping E and N, or writing metres where degrees belong, moves the file to another part of the world.
ED50 sources need one more step
If the source is ED50, resolve the ED50 to TUREF/WGS84 transformation safely first, and only then produce the WGS84 coordinates for the KML. Writing an old sheet's boundary straight into Google Earth produces something visually convincing and technically wrong.
Closure and simple quality control
The parcel polygon must close — the first and last coordinates identical — and a scrambled corner order makes the ring cross itself. After exporting, reopen the file and check the area and the visual position. Do not expect perfect agreement with road edges in the imagery; satellite imagery can carry an offset, which is one more reason it is not legal boundary evidence. Determining an official boundary is licensed survey engineering work; the app speeds up the field side and does not replace the side that signs.
Producing it in MapLab Survey
Open the parcel or working boundary in the project coordinate system, apply the needed transformation, and export as KML/KMZ. Put the source, date, method and coordinate system into the file description — that small note is what stops the wrong file being used in the field.
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
What is KML coordinate order?
Longitude, latitude, altitude.
Can TUREF coordinates be written directly to KML?
No. They must be transformed to WGS84 geographic coordinates first.
Is Google Earth a legal boundary base?
No. It is visual context.
KML or KMZ?
KMZ is a compressed package that can include KML and related assets.
Technical references
The field guidance in this article is aligned with the technical and official references below.
Related: Parcel query layer · Open KML on phone · ED50 to TUREF · MapLab Survey