How Istanbul's Duplicate Image Problem Got So Bad — And What Brought It to a Head

Istanbul's municipal digital archive holds tens of thousands of photographs. The problem, archivists and data managers have long complained internally, is that a significant portion of them appear more than once — sometimes under different file names, different dates, and different subject tags. The Istanbul Metropolitan Municipality's documentation directorate began a formal audit of its image holdings in early 2025, and the preliminary findings forced the question that nobody had wanted to answer: how did it get this bad?

The timing matters. The municipality, under Mayor Ekrem İmamoğlu and the CHP, has staked considerable political capital on open governance and data transparency — promises that look hollow when the city's own visual records are in disorder. A clean, reliable image database underpins everything from public communications to urban planning documentation along the Bosphorus development corridor, where contested construction projects have generated their own paper — and photographic — trails.

A Fragmented System Built Over Two Decades

The root of the duplication problem runs back to the early 2000s, when individual directorates — transport, heritage, emergency management — each began building their own digital repositories without a shared taxonomy or central oversight. The Fatih and Beyoğlu district municipalities, which merged into the greater metropolitan structure over successive reorganisations, brought their own incompatible filing conventions with them. By the time Istanbul's BIMTAS technology subsidiary attempted a partial consolidation in 2018, the foundational inconsistencies were already deeply embedded.

The 2023 Kahramanmaraş earthquakes added pressure nobody anticipated. Emergency documentation teams dispatched to assess Istanbul's own at-risk structures — particularly in older neighbourhoods like Avcılar and Zeytinburnu, both flagged in seismic risk surveys — produced thousands of new field photographs. Those images were uploaded rapidly, under crisis conditions, with minimal metadata discipline. A single damaged building in Zeytinburnu, photographed by three separate inspection teams on the same day in March 2023, ended up with eleven distinct file entries across four different directories.

Tourism added another layer of complexity. The Culture and Tourism Directorate, operating partly in coordination with the Turkish Ministry of Culture and Tourism and partly under municipal authority, runs its own promotional image library covering sites from the Süleymaniye Mosque to the Grand Bazaar. Cross-uploads between that library and the main municipal archive — never governed by a formal data-sharing protocol — seeded hundreds of additional duplicates throughout the 2019–2024 period.

What the Audit Found, and What Comes Next

The 2025 audit, conducted with technical support from Istanbul Teknik Üniversitesi's informatics department, identified duplicate or near-duplicate image pairs running into the thousands across the central archive alone. District-level repositories were not included in the first phase. The audit report, completed in the final quarter of 2025, recommended adopting a perceptual hashing protocol — a standard image-fingerprinting technique used by major European municipal archives including those in Amsterdam and Berlin — to identify near-identical files regardless of file name or format.

Implementation began in January 2026. The municipality set a target of reducing confirmed duplicates by 70 percent before the end of the year, with a unified metadata standard — based partly on the Dublin Core framework — rolled out across all directorates by September 2026. BIMTAS is managing the technical migration.

For residents and journalists who rely on the public-facing image portal, the practical difference will be searchability. A researcher trying to document, say, the construction history of the Galataport cruise terminal on the Karaköy waterfront has until now encountered the same archival image surfacing under as many as six different search queries. That is the most visible symptom of a problem that, at its core, is about institutional coordination — or the lack of it — across a city of 16 million people and two decades of unmanaged digital growth. The fix is unglamorous. It is also long overdue.