Sydney's Duplicate Image Problem: How the City Stacks Up Against London, Singapore and New York

Sydney's public agencies and cultural institutions are sitting on millions of duplicate digital images — redundant files clogging storage systems, slowing heritage assessments and complicating development approvals — and a patchwork of responses is emerging across the city just as peer cities in London, Singapore and New York have begun rolling out coordinated deduplication programs.

The problem has sharpened this year because several NSW government bodies are mid-migration: the NSW State Archives and Records Authority is consolidating legacy databases, the City of Sydney Council's development application portal handles thousands of image uploads per month, and the State Library of NSW on Macquarie Street holds a digitised photographic collection that archivists have publicly described as containing significant duplication across its colonial-era holdings. The intersection of those three pressures is forcing the question of how, exactly, institutions handle images that appear more than once in a system — and whether that handling is systematic or ad hoc.

What Sydney Is Actually Doing

The most visible local effort sits inside the Department of Planning, Housing and Infrastructure's ePlanning platform, which processes development applications across greater Sydney including high-volume corridors like Parramatta Road and the North West Growth Area centred on Box Hill. Staff there have been working since late 2025 on automated flagging of duplicate site photographs submitted by applicants — a routine frustration when the same image appears across dozens of staged DA submissions for a single subdivision.

The State Library's approach is different and slower. Its digitisation unit, based in the Macquarie Street building, relies partly on manual review for its photographic collections, supplemented by perceptual hashing software introduced in a 2023 upgrade. Perceptual hashing assigns a fingerprint to each image and matches near-identical files even when filenames differ — a meaningful step up from exact-match tools. The library has not publicly reported a completion date for its deduplication backlog.

At the local government level, the picture is uneven. Councils covering the inner west — including Marrickville and Leichhardt — use the NSW government's shared ePlanning infrastructure and therefore inherit whatever deduplication logic sits in that system. Outer suburban councils running older proprietary document management software are effectively handling the problem manually, if at all.

How Sydney Compares Abroad

London's response has been the most structured. The Greater London Authority mandated in January 2025 that all planning portals across its 32 boroughs integrate hash-based deduplication by the end of that calendar year, with a compliance audit scheduled for March 2026. Transport for London's asset management division completed a similar exercise across its infrastructure photo library — estimated at more than 4 million images — in mid-2024.

Singapore's Urban Redevelopment Authority went further still, embedding deduplication directly into its GovTech cloud storage layer so that duplicates are rejected at upload rather than caught after the fact. That upstream approach means the problem rarely accumulates. New York City's approach through its Department of City Planning uses a hybrid: automated flagging for new submissions combined with a rolling annual audit of legacy scans, a model that has reduced storage costs in its digital archive by a reported 18 percent since 2023, according to a budget submission the department filed with the City Council last year.

Sydney's challenge is structural. Unlike Singapore's centralised GovTech architecture or London's GLA mandate, NSW distributes responsibility across councils, state agencies and statutory bodies without a single authority setting a deduplication standard. That gap is not hypothetical — it shows up in storage budgets, in the time heritage assessors spend verifying whether two images are genuinely the same photograph taken from different sources, and in the accuracy of public-facing archives.

For residents and developers, the practical implication is straightforward: DA submissions in suburbs like Kellyville or Leppington that include duplicate images can trigger requests for additional information, adding days or weeks to assessment timelines. The NSW government's housing agenda, already under political pressure heading into 2027, depends in part on faster approvals — which means back-end data hygiene is no longer just an archivists' concern. Planning bodies and councils that have not yet reviewed their image management workflows have a reasonable deadline to consider: the ePlanning platform's next scheduled infrastructure update is due in the fourth quarter of 2026, and that window represents the clearest opportunity to embed upstream deduplication before another year of submissions accumulates.