Istanbul Grapples With Duplicate Image Problem in Digital Archives — and Lags Behind Istanbul's Rivals

Istanbul's municipal digital archives contain an estimated 40,000 to 60,000 duplicate or near-duplicate photographs spread across at least three separate public databases — a sprawl that has frustrated researchers, slowed heritage documentation projects, and complicated urban planning reviews tied to earthquake retrofitting work along the Marmara fault zone. The problem, long acknowledged internally by archivists but rarely discussed publicly, has taken on new urgency as the Istanbul Metropolitan Municipality attempts to digitise historic neighbourhood surveys across Fatih, Balat, and Eminönü ahead of a 2027 UNESCO reporting deadline.

The stakes are higher than they might seem. After the February 2023 Kahramanmaraş earthquakes killed more than 50,000 people across southern Turkey, municipal authorities accelerated structural risk mapping across Istanbul's older districts. That mapping process depends heavily on accurate photographic records of buildings — their facades, load-bearing walls, past renovation work. When duplicate images flood a database, automated tagging systems misfire, records get mismatched to wrong addresses, and field engineers waste hours cross-referencing analogue files held at separate institutions.

What Istanbul's Cultural Institutions Are Actually Doing

The Istanbul Research Institute, based in Beyoğlu on Meşrutiyet Caddesi, has been running a deduplication pilot since late 2024 using open-source perceptual hashing tools. The institute holds roughly 120,000 digitised images related to Istanbul's built environment, and project archivists have so far processed about a third of the collection. The work is painstaking: automated tools flag candidates, but human reviewers must confirm whether two near-identical images are true duplicates or distinct photographs taken seconds apart — a distinction that matters when documenting incremental changes to a building facade over decades.

Salt Araştırma, the research centre and archive operated by Garanti BBVA in Karaköy, adopted a more aggressive deduplication protocol in 2023 when it migrated its collections to a new content management system. Salt holds one of the most significant photographic archives in the city, including the Ara Güler negatives collection. Staff there use a combination of metadata reconciliation and visual similarity scoring, a workflow that took roughly 18 months to implement across approximately 200,000 records.

Neither institution publicly claims to have solved the problem. The Metropolitan Municipality's own digital library, accessible via the IBB portal, still shows visible duplication in its historic map and photograph sections — a situation any user searching for pre-1950 images of Galata or Üsküdar will encounter within minutes.

How Istanbul Compares to Amsterdam, Seoul, and Barcelona

Other cities with comparably dense heritage photo collections have moved faster. Amsterdam's Stadsarchief completed a full deduplication pass of its 800,000-image collection in 2022 using a combination of machine learning classifiers and crowdsourced verification, cutting duplicate records by roughly 18 percent according to the archive's own published report. Seoul's National Folk Museum completed a similar exercise across 1.2 million digitised items between 2021 and 2023, integrating deduplication directly into its ingest pipeline so new uploads are checked against existing records before they enter the live database. Barcelona's ICUB cultural institute began mandatory deduplication audits for all municipal cultural bodies in January 2025 as part of a broader open-data reform.

Istanbul's fragmented institutional landscape makes a unified approach harder. Unlike Amsterdam, where a single Stadsarchief holds the dominant municipal collection, Istanbul's photographic heritage is split between the IBB, Salt, the Istanbul Research Institute, the Atatürk Library in Taksim, and several university collections. No single body has the mandate or the budget to coordinate deduplication across all of them.

A coordinated framework, if one ever materialises, would likely fall under the IBB's digital transformation directorate, which has set a target of completing metadata standardisation across its own holdings by the end of 2026. Whether that timeline holds — given parallel pressures from earthquake risk work, tourism infrastructure upgrades along the Bosphorus, and ongoing disputes between the CHP-led municipality and the central government over project funding — remains an open institutional question.

For researchers and urban planners working in Istanbul right now, the practical advice is blunt: always cross-reference IBB portal images against Salt Araştırma's independently maintained catalogue before drawing conclusions from photographic evidence. Until a coordinated deduplication effort produces a shared identifier system, the two databases checking each other is the closest thing available to quality control.