Istanbul's Duplicate Image Problem: How the City Stacks Up Against Amsterdam, Seoul and Cairo

Istanbul's metropolitan administration confirmed earlier this year that its urban documentation database — used by planners, heritage officials and earthquake-preparedness teams alike — contains tens of thousands of duplicate photographic records, a bureaucratic tangle that is slowing infrastructure assessments across districts from Kadıköy to Eyüp Sultan. The problem is not unique to this city, but the stakes here are unusually high: post-2023 earthquake risk assessments depend heavily on accurate, deduplicated imagery of aging building stock.

The timing matters because Istanbul Municipality, operating under Mayor Ekrem İmamoğlu's CHP-led administration, has been pushing a broad digital transformation of city services since 2019. Part of that effort involves consolidating legacy image archives from older IBB departments into a single georeferenced system. When those archives were merged, duplicate images — sometimes four or five versions of the same façade, shot on different dates by different contractors — began clogging the database, making automated damage-detection algorithms unreliable.

What Other Cities Have Done

Amsterdam's municipal government completed a large-scale deduplication of its urban imagery archive in 2023, using perceptual hashing — a technique that assigns a numeric fingerprint to each image and flags near-identical copies — across roughly 2.4 million street-level photographs held by the city's spatial data unit. Seoul's Smart City Division deployed a similar system for its Digital Twin project, reducing redundant records by an estimated 30 percent in pilot districts before citywide rollout in 2024. Cairo, dealing with a comparable legacy-data problem tied to its historic-centre documentation efforts along the al-Muizz corridor, has moved more slowly, still relying on manual review teams as of early 2026.

Istanbul sits somewhere between Seoul's systematic approach and Cairo's manual slog. The IBB's Geographic Information Systems directorate — based in the Saraçhane administrative complex near Fatih — has contracted a Turkish technology firm to run hash-based deduplication across the archive, a process that began in March 2026. The Bosphorus Development Coordination Office, which oversees documentation tied to contested waterfront projects from Beşiktaş to Üsküdar, has its own parallel image library that has not yet been integrated into the main IBB system, creating a second layer of duplication risk.

Why Earthquake Readiness Adds Urgency

Turkey's Disaster and Emergency Management Authority, AFAD, requires municipalities in high-risk seismic zones to maintain verified, timestamped photographic records of buildings in urban renewal areas. Istanbul has more than 1,500 designated urban renewal zones, concentrated heavily in Bağcılar, Zeytinburnu and Avcılar — all districts underlain by soil types that amplify seismic shaking. When an image database contains duplicates flagged as distinct records, automated compliance checks can return false positives, suggesting a building has been inspected more recently than it actually has.

The deduplication contract signed by IBB in February 2026 is valued at approximately 18 million Turkish lira — a figure that reflects both the scale of the archive and the accelerating cost of IT procurement as inflation keeps software licensing prices volatile. For context, Amsterdam's comparable 2023 project cost roughly €400,000, covering a city with about one-quarter of Istanbul's urban footprint.

For property owners and developers waiting on permits in areas like the Galata–Karaköy heritage corridor, the practical consequence is delay. Permit applications that require cross-referencing building imagery against the IBB archive have been taking four to six weeks longer than the stated processing target, according to publicly available IBB service-standard reports for the first quarter of 2026.

The IBB's GIS team has set an internal deadline of October 2026 to complete the first deduplication pass across the core archive. Whether the Bosphorus Development Coordination Office's separate library gets folded in before year-end remains an open question — one that engineers and heritage preservation groups in the Boğaziçi Kıyı Şeridi protection zone are watching closely. If Istanbul wants to match Amsterdam's clean-slate model, the clock is running.