Privacy & sensitive locations
Coordinates are personal data: re-identification risk, geomasking, aggregation thresholds and the checks to run before a release.
A coordinate that describes a person is personal data, and it is unusually identifying: home locations are nearly unique, and a handful of visited places is enough to re-identify somebody from an otherwise anonymous track.
The dangerous part is that the standard defences feel stronger than they are. Aggregation is not anonymisation until a minimum count is enforced — a grid cell with one record in it names that record, and publishing the grid publishes the person. Rounding coordinates is a grid by another name. Random displacement protects a point and not a pattern, because an attacker with the underlying population can undo it. Even a heatmap of enough points reconstructs the points.
Below: the concepts cover re-identification risk and what each technique actually protects against; the how-to guides implement masking, aggregation and thresholds; and the fixes are the releases that leaked despite one of them.
🧭 Start with the concepts
The ideas the how-to guides below assume you already have.
⚙️ Then do the task
Step-by-step walkthroughs with code you can copy and adapt.
- How to measure re-identification risk in a point dataset
- How to apply donut geomasking to sensitive points in Python
- How to aggregate points to units that meet a minimum count
- How to suppress small counts in a spatial table in Python
- How to add differentially private noise to spatial counts
- How to reduce coordinate precision safely in Python
🔧 When it breaks
The errors this topic produces, with the cause explained rather than just the command.
- Geomasked points land in the sea or outside the study area
- Anonymised points still identify individuals
- Suppressed cells can be recovered from the totals
- Geomasking changed the result of the analysis
- A shared file still contains the original coordinates
- Why Are So Many of My Crime Points in Exactly the Same Place?
Show every fix in this topic
Learning paths through this topic
A curated route rather than a list — the guides in the order that builds on itself.
Related topics
Subjects that keep coming up alongside this one, most overlap first.