01The Source of Truth for Every Figure
Wherever a country's land registry publishes its own officially recorded parcel area, that is the number ALP shows. We do not recalculate or override a registered figure with our own estimate. Our own geometry-based measurement only ever runs where a registry does not publish a stated area for that parcel, and it is computed directly from the parcel's real boundary - never guessed, never carried over from a similar-looking parcel nearby.
02Projection & Geometric Consistency
Area, perimeter, and distance to a road or a zoning boundary are frequent sources of silently wrong numbers in GIS tooling, almost always because a calculation ran on raw latitude/longitude degrees instead of a real metric projection, or because two layers were compared in two different coordinate systems without anyone noticing. ALP never does either. In France, every one of those calculations runs in Lambert-93, the French national geodetic grid used by notaires and government services themselves. Outside France, we use a projection centred precisely on each parcel's own municipality, a standard surveying technique kept within a documented sub-1% distortion bound at that scale - well inside the resolution of the underlying registries. A parcel's boundary and the zoning boundary it is tested against are always resolved in the same coordinate system in the same calculation, so a zone classification cannot be wrong because the two layers were secretly misaligned.
03Exports Stay Metric
Every GeoJSON, KML or DXF export is written in a real surveying coordinate system, not raw degrees: the correct UTM zone for that parcel's own longitude, or the country's own official grid where one exists (Poland's PUWG 1992, France's Lambert-93). A file opens to scale in AutoCAD or QGIS without a manual reprojection step first.
04Freshness & Update Cycles
France, our only market with full-depth coverage today, is kept current automatically: a commune's cadastral boundaries, buildings, roads, zoning and recorded sale prices are re-harvested on a weekly cycle once you have looked it up once, rather than frozen at whatever they were the first time. Building permits (SDES Sitadel) refresh monthly, because that is how often the French government itself republishes the dataset, not a limit we impose. Every other covered country reflects the date we first analysed that municipality; continuous re-sync for those markets is on our roadmap but not live yet, and the product says so rather than presenting week-old data as current.
05What We Will Not Do
We do not fabricate a figure to fill a blank field. If a feature is mapped only as a point with no footprint polygon, we leave its area out rather than invent a plausible-looking number. If a zoning layer genuinely does not exist yet for a parcel, the record says so rather than defaulting to a guess. We only bring a new country's data online once its commercial reuse terms are confirmed in writing with the source - we would rather pause an expansion than publish parcels under licensing terms we have not actually cleared.
06Scope of This Page
This page describes how ALP's data pipeline is built to behave, and is kept in step with our own source code rather than written once and left to drift. It is not a substitute for your own professional verification before a binding transaction - always confirm a figure that a deal turns on against the official registry directly. Which countries currently have full, partial or pending coverage, and what each one includes, is listed on our Coverage page rather than restated here, so that page stays the one place that can go out of date.