Istanbul's Battle Against Duplicate Images in Its Digital Heritage Archive Lags Behind Amsterdam and Seoul

Turkey's largest cultural digitisation push is producing a problem nobody planned for: thousands of duplicate photographs, scanned maps and architectural drawings clogging the Istanbul Metropolitan Municipality's open-data archive, slowing researcher access and inflating storage costs at a moment when the city's tech budget is already under pressure from lira depreciation.

The IBB Digital Archive, which covers materials from Sultanahmet to the historic wharves of Karaköy, had accumulated more than 1.4 million image files as of the end of 2025, according to figures published on the municipality's open-data portal. Archive staff acknowledge internally that a significant share of those files are exact or near-exact duplicates — the result of multiple scanning rounds, contributor uploads and bulk transfers from district municipalities including Fatih and Beyoğlu.

How Istanbul Compares to Amsterdam and Seoul

Amsterdam's Stadsarchief completed a deduplication sweep of its own 2.1-million-image collection in 2023, using perceptual hashing software — a technique that identifies visually identical or near-identical images even when file names differ. The Dutch archive reported removing roughly 180,000 redundant files in a single three-month operation, cutting annual cloud storage spending by an estimated 12 percent. Seoul's National Folk Museum ran a comparable programme in early 2024, clearing duplicates from its digitised textile and ceramics catalogue using open-source tooling developed at Korea Advanced Institute of Science and Technology.

Istanbul has no equivalent programme running yet. The Istanbul Research Institute, based on İstiklal Caddesi in Beyoğlu, operates its own separate image collection focused on pre-Republican and early Republican-era photography and has discussed deduplication workflows internally, but has not launched a formal automated sweep. The SALT Research centre, which holds extensive records on modern Turkish architecture and holds a reading room in Galata, uses a commercial digital asset management system that includes basic duplicate flagging — though staff describe it as a manual review process rather than a batch automated one.

The stakes are not purely administrative. With Istanbul facing renewed urgency around earthquake preparedness following the 2023 Kahramanmaras disaster, accurate and accessible architectural records of older districts — Balat, Fener, Zeyrek — carry direct structural significance. Duplicate and misfiled images slow down the kind of rapid cross-referencing that engineers and conservation officers need when assessing vulnerable buildings.

Why the Gap Exists, and What It Would Take to Close It

Part of the problem is institutional fragmentation. The IBB archive, the Istanbul Research Institute, SALT Galata and the separately administered Atatürk Library on Millet Caddesi in Fatih each maintain independent repositories with different metadata standards and file naming conventions. That makes cross-institutional deduplication — the kind Amsterdam performed centrally — technically and politically complicated in Istanbul's environment, where the CHP-run municipality and various state-aligned cultural bodies do not always coordinate smoothly.

Open-source tools capable of handling the job exist and are free. PhotoDNA, developed by Microsoft, is used by major European national archives. Python-based libraries such as imagededup can process tens of thousands of files on commodity hardware in hours. The barrier in Istanbul is not cost or availability — it is the absence of a lead institution willing to own the process across competing archives.

Researchers and heritage professionals who regularly use Istanbul's digital collections have long noted the problem in academic literature, pointing to duplicate scans of the same Bosphorus waterfront surveys appearing under different catalogue numbers across multiple portals. One 2024 paper published in the Journal of Documentation cited Istanbul's fragmented archive ecosystem as a case study in what the authors described as institutional silo effects in municipal digitisation projects.

For anyone using the IBB open-data portal or the Istanbul Research Institute's online catalogue right now, the practical advice is straightforward: search by subject keyword rather than browsing by file date, since duplicate entries tend to cluster by upload batch. The IBB portal's advanced filter allows users to narrow results by contributing institution, which reduces duplicate returns in practice even without a formal deduplication layer. Whether the city will launch a coordinated programme before the archive doubles in size again — a plausible outcome given current scanning rates — is a question the institutions involved have not yet answered publicly.