Istanbul's Street Archives Tackle Massive Duplicate Problem After Rushed Digitization

Istanbul's official digital image archive, covering everything from Ottoman-era facades in Sultanahmet to post-earthquake structural surveys in the Fatih district, contains tens of thousands of duplicate photographs, a problem that accumulated quietly over roughly two decades of poorly coordinated digitisation work and is now forcing a wholesale review of how the city stores and uses its own visual records.

The issue matters acutely in 2026 because Istanbul is mid-way through a seismic risk reassessment programme launched in the wake of the February 2023 Kahramanmaraş earthquakes. City planners and engineers at the Istanbul Metropolitan Municipality's Directorate of Earthquake Risk Management rely on photographic documentation to track building conditions across high-risk neighbourhoods such as Zeytinburnu, Bağcılar, and Küçükçekmece. When the same image appears multiple times under different file names and timestamps, assessments can be skewed and resources misdirected.

Three Separate Systems, One Chaotic Result

The roots of the problem stretch back to at least 2004, when the municipality contracted separate vendors to digitise street-level survey photography for the Historic Peninsula conservation zone. A parallel project run by İBB's urban planning arm, then operating under different political leadership, used incompatible metadata standards. A third wave of uploads came after the 2013 Gezi Park protests, when the city rushed to document public spaces across Beyoğlu and Taksim as part of a broader urban inventory effort. None of the three systems talked to each other. By the time a unified platform was attempted around 2019, the damage was baked in: an internal review conducted by İBB's information technology department found that roughly 34 percent of images in the central repository were either exact duplicates or near-identical frames from the same shoot, according to municipal documents reviewed by The Daily Istanbul.

The Istanbul Foundation for Culture and Arts, known by its Turkish acronym İKSV, flagged a narrower version of this problem as far back as 2017 when curating materials for an exhibition on Boğaziçi waterfront development. Researchers found multiple near-identical aerial photographs of the Rumelihisarı shoreline catalogued under different acquisition dates, making it impossible to establish a reliable timeline of shoreline changes. The foundation flagged the inconsistency in a written submission to the municipality's heritage directorate, but no systematic audit followed at the time.

Why the Fix Is Harder Than It Sounds

Removing duplicate images from a live municipal archive is not a simple delete operation. Many duplicates are embedded in legal documents, building permits, court filings over demolition orders in neighbourhoods like Tarlabaşı, expropriation records along the Kanal İstanbul corridor. Deleting a file without tracing every reference to it risks breaking evidentiary chains in active legal proceedings. The municipality's legal affairs office has reportedly been cautious for precisely this reason, slowing what might otherwise be a straightforward technical cleanup.

Istanbul Technical University's Department of Geomatics Engineering has been running a pilot deduplication project since March 2026, applying perceptual hashing algorithms to roughly 200,000 images drawn from the Fatih and Beyoğlu district archives. The work is being done under a memorandum of understanding with İBB and is expected to produce a methodology report by October 2026. If the pilot proves successful, a citywide rollout affecting an estimated 1.4 million archived images could begin in the first quarter of 2027.

For residents and preservation advocates in neighbourhoods such as Balat and Fener, where documentation of historic timber-frame yalı buildings is essential for heritage grant applications, the practical stakes are immediate. An application to the General Directorate of Foundations for restoration funding requires verified photographic evidence. Duplicate or misdated images can trigger automatic rejection. Several community groups in Fener have already reported delays of six months or more tracing approved imagery back through the municipal system.

The October 2026 methodology report from İTÜ will be the clearest signal yet of whether the city has found a workable path through the problem. Until then, architects, engineers, and heritage professionals working across the city are advised to cross-reference any municipally sourced images against the Land Registry and Cadastre Directorate's independently maintained photograph logs, which were digitised later and under a single vendor contract, making them, for now, the cleaner of the city's two main visual databases.