Istanbul's War on Duplicate Images: How the City Stacks Up Against Rome, Barcelona and Seoul

Istanbul's official tourism and municipal portals carry thousands of photographs — and a growing number of them are the same image filed twice, sometimes under different names, sometimes under different neighbourhoods altogether. The Istanbul Metropolitan Municipality's digital content office confirmed earlier this year that an internal audit was underway across its GIS-linked photo databases, which serve everything from the IBB (Istanbul Büyükşehir Belediyesi) neighbourhood information portals to the city's tourism-facing platforms maintained in partnership with the Ministry of Culture and Tourism. The audit, which began in the first quarter of 2026, was triggered after residents filing planning objections near Karaköy discovered the same aerial photograph had been registered under two separate cadastral zones.

The problem is not trivial. Cities run on visual data. Duplicate images in municipal archives distort everything from heritage assessments to earthquake-risk building surveys — and Istanbul, still absorbing the administrative lessons of the 2023 Kahramanmaraş earthquakes that killed more than 50,000 people across southern Turkey, cannot afford ambiguity in its urban documentation. The IBB has been pushing a broad digital transformation program since 2020, but inherited databases built across decades of inconsistent IT procurement mean the deduplication challenge is structural, not cosmetic.

How Other Cities Are Handling It

Rome's municipal archive, the Archivio Fotografico Comunale, completed a three-year deduplication project in 2024 that removed roughly 34,000 redundant image files from its public-access Capitoline collections — a figure the project team published in a March 2025 proceedings paper from the Sapienza University digital humanities faculty. Barcelona's urban data office, working under the city's Smart City initiative centered on the 22@ district in Poblenou, deployed perceptual hashing software in 2023 and reported cutting duplicate imagery in its open data portal by around 40 percent within 18 months. Seoul's Smart City Division, operating out of the Digital Mayor's Office established in 2022, integrated AI-assisted deduplication directly into upload workflows, meaning duplicates are now flagged before they enter the archive rather than after.

Istanbul is effectively still in the before-not-after phase. The IBB's ongoing audit covers the Tarihi Yarımada — the historic peninsula encompassing Sultanahmet and the Grand Bazaar area — as a priority zone, given the density of heritage structures and the frequency with which tourist-facing agencies and municipal planners draw on the same photographic sources. The Fatih district's planning department, which oversees much of that zone, is cross-referencing its own holdings against the central IBB database. Officials have not yet published a figure for how many duplicates have been identified, but the audit timeline runs to the end of the third quarter of 2026.

Why Istanbul's Geography Makes This Harder

Istanbul's split across two continents — and the administrative complexity of 39 distinct district municipalities operating under the metropolitan umbrella — means photo records for a single street can exist in multiple siloed databases. A photograph of, say, Bağcılar's urban renewal blocks or the Galata Tower's immediate surroundings in Beyoğlu might sit in the IBB central archive, in the relevant district municipality's own system, in a tourism ministry server, and on a contracted agency's cloud storage, each with slightly different metadata. That redundancy was once seen as a backup feature. It is now recognised as a liability.

Consultants working on the EU-funded UR-HERITAG project, which involves Istanbul alongside several other southeastern European cities and runs through December 2026, have flagged deduplication as a prerequisite for any reliable digital-twin modelling of heritage zones. Digital twin infrastructure requires clean, non-redundant visual data as a baseline — something Rome and Barcelona have a meaningful head start on.

The practical next step for Istanbul's residents and urban professionals is to treat the IBB's open data portal with calibrated scepticism until the audit concludes, expected by September 2026. Developers and architects submitting planning applications for sites in Karaköy, Kadıköy or any of the districts flagged in the heritage overlay zones should independently verify photographic evidence rather than relying solely on municipal image databases. The IBB has said it will publish an updated metadata standard for image submissions once the audit phase ends — a move that, if it mirrors Barcelona's approach, should at minimum prevent the problem from compounding further.