Istanbul's Duplicate Image Problem: How the City Stacks Up Against Rome, Barcelona and Cairo

Istanbul's municipal digital archive now holds an estimated several million photographs of historic sites, infrastructure, and public spaces, a sprawling repository built across decades of overlapping digitisation drives by agencies that rarely spoke to one another. The problem: a significant share of those images are duplicates, near-duplicates, or misattributed files that slow down archivists, inflate storage costs, and — in the case of heritage assets along the Bosphorus — risk embedding factual errors into planning documents that inform earthquake-resilience reviews.

The issue has sharpened this year because Istanbul Metropolitan Municipality's BIMTAS unit, the city's technical research and infrastructure arm, is mid-way through a project to cross-reference pre- and post-2023 Kahramanmaras earthquake structural surveys with photographic evidence of at-risk buildings across districts including Fatih, Zeytinburnu, and Bakırköy. When duplicate or mislabelled images enter that workflow, the consequences are not merely administrative.

What Istanbul Is Actually Doing

The municipality has been piloting a perceptual hash-based deduplication system — a technique that detects visually identical images even when file names or metadata differ — through a tender awarded in late 2025. The contract, handled through the municipality's IT directorate, targets the photographic holdings of the Istanbul Archaeological Museums on Osman Hamdi Bey Yokuşu in Sultanahmet, as well as the Atatürk Library on Millet Caddesi in Beyoğlu, both of which completed major scanning drives between 2021 and 2024. The Atatürk Library alone added more than 400,000 digitised items to its public portal during that period, according to figures cited in municipal budget presentations reviewed for this article.

Staff at smaller neighbourhood-level cultural houses — including those run by the Kadıköy and Beşiktaş district municipalities — continue to manage photo collections largely manually, cross-checking against the central BIMTAS catalogue by hand. That gap between the main municipality and the 39 district municipalities is precisely where redundant images pile up undetected.

How That Compares With Rome, Barcelona, and Cairo

Rome's Sovrintendenza Capitolina, which manages photographic documentation of the capital's archaeological zones, began rolling out automated deduplication across its digitised collections in 2023, integrating the process directly into its FIAF-aligned cataloguing system. Barcelona's Institut de Cultura, which oversees the city's municipal archives at the Arxiu Fotogràfic on Plaça de Pons i Clerch, went further and published an open-data deduplication protocol in January 2025 that other Catalan municipalities can adopt at no licensing cost. Cairo's Egyptian Heritage Rescue Foundation has tackled a related problem — mass duplicate scanning of papyri and manuscript pages — by partnering with international university labs, though the city's municipal photo archives remain more fragmented than Istanbul's.

The practical gap between Istanbul and Barcelona is instructive. Barcelona's system flags potential duplicates at the point of ingest, before an image enters the main archive. Istanbul's current pilot, by contrast, runs deduplication as a retrospective clean-up on material already stored. That sequencing matters for cost: storage on municipal servers is not free, and retrospective deduplication requires a separate processing round that adds staff hours. Rome sits somewhere in between, having retrofitted its system into an existing workflow rather than redesigning ingest from scratch.

Istanbul's total digitised cultural photograph collection across all major institutions is difficult to pin down precisely because the district municipalities do not report centrally. BIMTAS figures presented to the city council in March 2026 referenced a combined holding of over three million indexed image files across the institutions directly under metropolitan authority — a number widely cited in local heritage circles as an undercount once district holdings are included.

For researchers, photographers, and urban planners working with Istanbul's image archives right now, the practical advice is to cross-check any photograph retrieved from the Atatürk Library portal against the Istanbul Archaeological Museums' separate online catalogue before using it in a formal document, since the two collections overlap substantially in their coverage of the Historic Peninsula. The BIMTAS deduplication project is scheduled to complete its first full validation pass by the end of 2026, at which point a consolidated search interface is expected to go live — giving both professional users and the public a single point of entry to a cleaner, better-labelled visual record of one of the world's most photographed cities.