Zurich's Duplicate Image Problem: What Happens Next and the Key Decisions Ahead

Zurich's cantonal authorities face a concrete reckoning over how to clean up sprawling digital image archives that have accumulated duplicate, near-duplicate and misclassified files across at least three major public databases. The problem is not abstract: city planners at the Stadtplanung Zürich office on Amtshaus I have flagged the issue internally, and administrators at the Stadtarchiv on Neumarkt 4 are weighing options that carry real financial and legal consequences.

The timing matters. The UBS integration of Credit Suisse assets has brought renewed scrutiny to Swiss data governance standards across the financial and public sectors alike. Cantonal and federal regulators have signaled that institutions handling sensitive imagery — from building surveys to urban planning overlays — must align with updated federal data management protocols by the end of 2026. Missing that window risks sanctions and, more practically, a freeze on grant funding tied to ETH Zurich's Smart Urban Lab partnership, which supports data infrastructure across Zurich's Kreis 5 and Kreis 9 districts.

Where the Files Are Piling Up

The duplicate image problem is concentrated in three systems. The Grundbuchamt — the land registry — holds property boundary surveys that have been scanned multiple times across different digitisation rounds since 2018. The Stadtarchiv's photographic collection, which covers everything from 1890s street photography to recent construction permits along Langstrasse, contains an estimated several thousand redundant entries, according to publicly available digitisation project summaries. The third node is the geographic information system maintained jointly by the Amt für Geoinformation and partners at ETH Zürich's Institute of Cartography and Geoinformation in Hönggerberg, where aerial survey images overlap without consistent metadata tagging.

The practical problem is not just wasted storage. Duplicate images create false records in search results, complicate legal discovery in property disputes and slow the automated planning tools that Zurich's building department relies on when processing the roughly 3,500 construction permit applications the city receives annually. For a housing market already under severe pressure — the city's residential vacancy rate has sat below 0.5 percent for several years running — delays in permit processing carry direct economic costs for developers and renters alike.

The Decisions That Cannot Wait

Three choices are now on the table. First, city administrators must decide whether to run a single centralised deduplication process across all three databases simultaneously, or tackle each system separately. A simultaneous approach carries integration risk but offers a one-time solution; a phased approach is slower but allows staff at each institution to validate results before the next system is touched.

Second, the Stadtarchiv must settle on a retention policy for near-duplicate images — files that are not identical but show the same subject with minor variation in angle or exposure. Archivists argue these have historical value. IT procurement officials counter that storage contracts with the city's data centre on Hagenholzstrasse cost money per terabyte, and that the bill grows every quarter the question stays open.

Third, and most consequential, is whether Zurich adopts an automated machine-learning deduplication tool or relies on manual review. The ETH Zurich Digital Humanities Lab has developed image-matching software tested on comparable municipal archives in Bern and Basel. Using that tool would accelerate the process significantly but requires a formal procurement decision — and under Swiss public procurement law, any contract above the CHF 230,000 threshold triggers a mandatory public tender process that alone takes a minimum of 40 days.

The cantonal deadline of December 31, 2026 is not generous. If procurement begins in August, the tender window alone eats into autumn. Stadtarchiv administrators and Amt für Geoinformation staff are expected to present a joint recommendation to the relevant cantonal directorate before the summer recess ends in mid-August. Whatever they decide, the window for a clean resolution before the federal data compliance deadline is narrowing fast.