Zurich Leads on Duplicate Image Removal, But Other Cities Are Closing the Gap

Zurich's cantonal geodata authority finalized a system-wide audit of its public digital planning portal in June 2026, clearing more than 14,000 duplicate image files that had accumulated since the platform's 2019 launch. The cleanup, overseen by the Amt für Raumentwicklung, affects property records, zoning overlays, and heritage documentation for neighborhoods stretching from Albisrieden to Schwamendingen.

The timing matters. European cities are under growing pressure to comply with the EU's updated Data Governance Act requirements, which came into force for associated non-member states — Switzerland included, under bilateral data accords — at the start of 2026. Duplicate records do not just waste server space; they create legal liability when contradictory images are cited in planning disputes or property valuations. In a city where a 3.5-room apartment in Kreis 4 routinely fetches upwards of CHF 800,000, a misfiled façade photograph attached to the wrong cadastral entry can carry real financial consequences.

What Zurich Is Actually Doing

The cantonal program uses a perceptual hashing algorithm — technology already common in commercial photo management — applied to the roughly 2.3 million images held across the Geoportal Kanton Zürich, the city's open-data infrastructure hosted at maps.zh.ch. When two images score above a 97 percent similarity threshold, a human reviewer at the Stadtentwicklung Zürich office on Amtshaus III signs off before any deletion. That human-in-the-loop requirement was added after a 2023 pilot mistakenly flagged before-and-after demolition photographs of a protected building in Hottingen as duplicates — images that were, in fact, legally distinct records.

The ETH Zurich spin-off Picterra, which specialises in geospatial image analysis, has provided technical consultation to the cantonal team, according to procurement documents published on simap.ch dated March 2026. The contract value listed in those documents is CHF 340,000 for an 18-month engagement covering algorithm calibration and staff training.

Amsterdam's municipal archive, the Stadsarchief Amsterdam, completed a comparable deduplication exercise in late 2024 across its 750,000-image historic building record. The Dutch project relied on a fully automated pipeline with no mandatory human review step — a choice that later prompted a formal complaint from the city's heritage preservation board after 47 canal-house images were incorrectly retired. Vienna's MA 41 geodata department is currently mid-project, having started its own audit in January 2026, and has publicly acknowledged borrowing methodological notes from Zurich's 2023 pilot documentation.

Where Other Cities Struggle

Singapore's Urban Redevelopment Authority manages one of the densest digital planning archives in Asia, covering more than 5,500 development applications filed annually. Its deduplication process, described in a 2025 government technology review, uses a commercial off-the-shelf solution rather than a bespoke system, and city officials there have noted publicly that cross-departmental image silos remain a persistent problem — something Zurich largely avoided by centralising its geodata under a single cantonal umbrella rather than leaving it fragmented across district administrations.

London presents a starker contrast. The 33 separate borough planning portals each maintain their own image repositories, with no unified deduplication standard across the Greater London Authority. A 2025 report by the Local Government Association found that duplicate imagery inflated storage costs at some boroughs by an estimated 18 to 22 percent annually, though it did not name individual councils.

Zurich is not finished. The Amt für Raumentwicklung has signaled, in its 2026–2028 work program published on zh.ch, that the next phase will extend deduplication checks to video walkthroughs and 3D point-cloud files submitted as part of building permit applications — a data type that no comparable European city administration has yet formally addressed at scale. Reviews of those file types are scheduled to begin in the first quarter of 2027. Property owners and architects submitting documentation through the eBau portal will face updated file-naming and metadata requirements from January 1, 2027, giving them roughly six months to adjust their submission workflows.