Istanbul's Digital Archives Are Riddled With Duplicate Images — Here's What the Numbers Actually Show

Roughly one in five image files stored across Istanbul's major municipal digital archives is a duplicate — an identical or near-identical photograph occupying server space, distorting search results, and, in several documented cases, replacing higher-resolution originals with compressed copies. That figure comes from an internal audit completed in May 2026 by the Istanbul Metropolitan Municipality's Digital Heritage Unit, which manages collections spanning everything from Ottoman-era architectural surveys to contemporary Bosphorus shoreline photography.

The timing matters. Istanbul is two years into a post-earthquake infrastructure review triggered by the February 2023 Kahramanmaraş disaster, and a significant portion of the city's building documentation — photographs of load-bearing walls, façade conditions, and neighbourhood streetscapes used by structural engineers — sits inside the same databases now flagged for redundancy problems. When a duplicate image replaces an original, particularly one taken at a different date or angle, the downstream consequences for urban planners and earthquake-risk assessors are not trivial.

The Scale of the Problem, District by District

The audit covered four primary repositories. The Istanbul Archaeological Museums digitisation project, headquartered near Sultanahmet, holds approximately 340,000 image files. The Atatürk Library on Taksim Square — which houses the city's largest public photograph collection — manages a separate database of around 210,000 items. Together, those two institutions account for the bulk of the flagged duplicates: roughly 87,000 files between them require human review, according to figures the Digital Heritage Unit submitted to the Metropolitan Municipality's cultural affairs committee in June 2026.

A third repository, maintained by the Fatih Municipality covering the historic peninsula, contains around 95,000 images linked to the UNESCO World Heritage buffer zone. Staff there identified a separate but related problem: roughly 3,400 files had been tagged with incorrect metadata when batch-uploaded between 2021 and 2023, meaning a photograph of a building on Divanyolu Caddesi might carry location data pointing to a site in Eyüpsultan. That error rate — about 3.6 percent of the Fatih collection — is modest by international standards but significant given the precision required for heritage protection work.

The issue is not purely bureaucratic. Storage costs for unmanaged municipal databases in Istanbul have risen sharply alongside inflation. Server leasing and cloud backup for the city's cultural institutions ran to approximately 14.2 million Turkish lira in 2025, up from around 9.8 million lira the previous year, partly because duplicate files inflate storage demand without adding any informational value. At current lira exchange rates that translated to a real-terms cost increase even before accounting for currency depreciation.

What Deduplication Actually Involves — and Who Pays

Automated deduplication software can flag near-identical images using perceptual hashing algorithms, but the final decision on which version to retain requires human judgment. A photograph taken in 2018 of a yalı on the Bosphorus and a retouched version of the same image uploaded in 2022 may hash as near-duplicates, but only a trained archivist can determine which preserves more visual information. The Digital Heritage Unit estimated in its May audit that clearing the backlog at the Atatürk Library alone would require around 1,400 staff-hours at current review speeds — the equivalent of roughly nine months of part-time archival labour.

Two technology vendors active in the Turkish public-sector market — both based in the Maslak business district — submitted proposals to the Metropolitan Municipality's procurement office in April 2026 offering semi-automated solutions. Neither contract had been awarded as of the audit's publication date. The delay reflects a broader procurement bottleneck: under current Treasury regulations, digital services contracts above 2 million lira require a competitive tender process that averages 90 to 120 days from announcement to award.

For researchers, journalists, or urban planners currently relying on these databases, the practical advice is straightforward. Cross-reference any image pulled from the Atatürk Library or the Fatih Municipality heritage portal against at least one secondary source — whether a printed catalogue, a separately held institutional archive, or the Istanbul Archaeological Museums' own reference collections on Osman Hamdi Bey Yokuşu — before treating it as a definitive record. The databases remain open and usable, but until the deduplication backlog clears, caveat downloader.