Zurich Takes a Systematic Approach to Duplicate Images in Public Records — Other Cities Are Still Catching Up

Zurich's city administration confirmed this spring that a structured review of duplicate images across its public-facing digital registers is underway, targeting everything from building permit portals to the official property and street-documentation databases maintained by the Stadtentwicklung Zürich office. The effort, which began in earnest in early 2026, is drawing quiet attention from municipal tech teams in Vienna, Amsterdam and Copenhagen who are facing versions of the same problem.

The issue matters more now because Swiss cantons are midway through a broader e-government harmonisation push, with the federal Confederation's digitalisation strategy requiring that cantonal and municipal records meet interoperability standards by the end of 2027. Duplicate or mismatched imagery inside geodata systems is not a cosmetic problem — it creates errors in automated planning reviews, skews AI-assisted housing assessments, and can delay building permit approvals in a city already under severe housing pressure. Zurich's Wohnungsnot crisis, with vacancy rates consistently below 0.1 percent in recent years, means any friction in the planning pipeline carries real cost.

Inside the city's own infrastructure, the Geomatik + Vermessung Zürich division — the municipal surveying and geomatics office based on Lindenbachstrasse — is leading the deduplication work alongside the Stadtarchiv, which holds decades of photographic documentation stretching back through the 20th century. The Stadtarchiv, housed near the Neumarkt in the Altstadt, digitised large portions of its holdings between 2018 and 2023, a process that introduced layered redundancies as images were ingested from multiple source formats. Staff there have identified clusters of near-identical images tagged under different reference numbers in the archive's metadata system, a problem compounded when older catalogue entries were merged with newer digital uploads.

What Zurich Is Doing Differently

The city is using perceptual hashing — a technique that generates a compact fingerprint for each image based on visual content rather than file metadata — to flag near-duplicate entries across databases. This is paired with manual review for anything touching listed buildings or entries tied to ongoing planning disputes. The approach is more resource-intensive than the fully automated purges that Hamburg and Berlin have run on their respective Geoportal systems, but city officials have argued, without specifying exact figures publicly, that the manual check layer reduces the risk of incorrectly removing legally significant documentation.

Vienna's MA 41 geodata service ran a comparable automated deduplication exercise across its Stadtplan Wien portal in 2024 and reported removing tens of thousands of redundant image records. Amsterdam's Stadsarchief has been more cautious, citing concerns about archival completeness, and has so far limited its deduplication work to post-2010 digital acquisitions. Copenhagen's approach mirrors Zurich's hybrid model most closely, though Denmark's centralized national geodata infrastructure — administered through the Danish Agency for Data Supply and Infrastructure — gives Copenhagen departments less autonomy than Zurich's cantonal system allows.

ETH Zurich's Chair of Geoinformation Engineering has been involved in advising the city's technical team, though the precise scope of that advisory relationship has not been disclosed publicly. The university's Hönggerberg campus hosts research into automated image analysis for urban systems, work that has relevance well beyond the archival problem.

What Comes Next for Residents and Planners

For ordinary Zürich residents navigating the online building permit portal — accessible via the Stadtentwicklung site and regularly used by architects and property owners in districts like Altstetten and Oerlikon — the practical result should be faster load times and more reliable image returns when searching property histories. The city's digital services team has indicated the first phase of the cleanup is expected to be complete before the end of the third quarter of 2026.

Architects and planning consultants working in the city should check whether any project files submitted before March 2025 contain image attachments flagged during the review process — the city has advised affected parties will be contacted directly. Those with pending applications tied to the Hochparterre-listed planning zones around Zürich West should confirm their documentation packages with their assigned case officer at Stadtentwicklung before the summer recess ends in August.