Istanbul Races to Purge Duplicate Images From Its Digital Heritage Archive — and Other Cities Are Watching

Istanbul's metropolitan municipality confirmed this spring that its central digital archive — used by planners, historians, and tourism agencies — contained tens of thousands of duplicate images, some files catalogued under three or four separate entries, clogging a system that underpins everything from earthquake-resilience planning to Bosphorus waterfront development permits. The cleanup effort, running since March 2026, has so far processed roughly 40 percent of the archive held at the Istanbul Metropolitan Municipality's (IBB) urban documentation unit in Fatih.

The timing matters. With Turkey still absorbing lessons from the February 2023 Kahramanmaraş earthquakes, municipal authorities have leaned heavily on photographic and geospatial image records to model structural risk across older districts. Duplicate entries don't just waste storage — they generate conflicting data sets that can skew risk assessments in neighbourhoods like Zeytinburnu and Avcılar, both flagged as high-priority seismic zones. A redundant image filed twice under different metadata tags can make a building appear twice in a survey count, distorting the figures planners rely on.

A Problem Shared — But Not Equally Solved

Istanbul is not alone. Rome's Sovraintendenza Capitolina reported in late 2024 that its digitised cultural-heritage image bank had an estimated duplication rate of around 18 percent, a figure that emerged during a European Union-funded audit. Amsterdam's city archive, the Stadsarchief, completed a machine-learning-assisted deduplication project in 2023, cutting its active image index by roughly 12 percent and freeing up significant server capacity. Both cities used automated perceptual-hash algorithms — software that compares images at a pixel-pattern level rather than relying on file names or metadata alone.

Istanbul's effort, by contrast, has relied more heavily on manual review, partly because the IBB archive mixes modern digital photographs with high-resolution scans of Ottoman-era prints and maps, many held at the Atatürk Library on Mete Caddesi in Beyoğlu. Perceptual-hash tools struggle with aged, discoloured, or variably scanned historical material, so human archivists have had to intervene at a granular level. That has slowed the pace and raised the cost. The IBB has not published an official budget figure for the project, but the municipality's 2026 digital-infrastructure allocation — approved in January — set aside 180 million Turkish lira for technology and data management across all departments.

The duplication problem also has a public-facing dimension. Istanbul's tourism promotion body, Istanbul Tanıtım Ajansı, maintains a separate image library used by travel media and licensing agencies. Staff there have described — without official attribution — a routine frustration with receiving the same heritage photograph catalogued under different landmark names, particularly for sites in Sultanahmet where the Blue Mosque, Hagia Sophia, and the Topkapı Palace grounds overlap geographically and historically. A single drone photograph taken above the Hippodrome, for instance, might be filed under all three landmarks simultaneously, creating three live entries where one should exist.

What the Next Six Months Look Like

The IBB has set an internal target of completing the first full deduplication pass by the end of September 2026, ahead of the autumn municipal planning cycle when updated imagery feeds into development-permit assessments along the Bosphorus corridor. Whether automated tools will be brought in for the second phase — covering the Ottoman-era scanned material — is still under internal discussion, according to public procurement notices posted to the municipality's website in June.

For residents and businesses that interact with the archive — property developers seeking historical comparison images, journalists pulling rights-cleared photographs, or school programmes using the digital collection — the practical advice is straightforward: cross-reference any image retrieved from the IBB portal against the Atatürk Library's own separately maintained catalogue, which is searchable online and has been subject to a stricter cataloguing protocol since 2021. Discrepancies between the two databases are, for now, a feature of the transition period rather than a permanent state. Rome took approximately 14 months to close that kind of gap after beginning its own cleanup. Amsterdam managed it in nine. Istanbul, working with a larger and more complex archive, is planning for twelve.