How the Diff Works

Our diffing tool allows you to compare two geospatial files (GeoJSON, GPKG, etc.) to quickly identify changes between them. The engine operates feature-by-feature, not pixel or geometry precision, so it detects whether an entire feature is present in the other file or not.

What the tool calculates

Added features: Features that exist in the "after" file but not in the "before" file.
Removed features: Features that exist in the "before" file but not in the "after" file.
Unchanged features: Features that exist in both files exactly (geometry matches).
Feature area: Computed in square meters for polygons/multipolygons.
Feature length: Computed for lines and multilines.
Point/MultiPoint features: Count only, visualized as added/removed/unchanged.

Supported Geometry Types

Geometry Type	What’s Calculated
Point	Count, visual highlight
MultiPoint	Count, visual highlight
LineString	Count, Length, visual highlight
MultiLineString	Count, Length, visual highlight
Polygon	Count, Area, visual highlight
MultiPolygon	Count, Area, visual highlight
GeometryCollection	Skipped in stats/display due to complexity

How the Diffing Engine Works

The engine takes two geospatial files: Before and After.
It compares each feature in the "Before" file against the "After" file by exact geometry.
If a feature exists in "After" but not "Before", it is marked Added.
If a feature exists in "Before" but not "After", it is marked Removed.
If a feature exists in both files with identical geometry, it is marked Unchanged.
Areas (for polygons) and lengths (for lines) are computed in projected coordinates for accuracy.
The engine ignores attributes/properties—any differences in metadata do not affect the diff.

Notes & Warnings

Large files (hundreds of MBs or GBs) may take a few seconds to process.
GeometryCollections are skipped and will not appear in counts or visualization.
The engine is feature-based, not geometry difference-based. Partial overlaps are not split.