How Helsinki's City Archive Ended Up With Thousands of Duplicate Digital Images — and What It Plans to Do About It

Helsinki's City Archive holds somewhere in the region of 1.2 million digitised photographs, maps and planning documents — but nobody is entirely sure how many of those files are exact or near-exact duplicates sitting silently on multiple servers. That uncertainty is the starting point for a quiet but consequential overhaul of the city's digital records management, now entering its operational phase in the summer of 2026.

The problem did not appear overnight. It accumulated over roughly ten years as individual city departments — from the Helsinki City Planning Department on Kansakoulukatu to the heritage teams at the Hakasalmi Villa museum complex — ran their own scanning drives with their own naming conventions and their own storage solutions. When those siloed collections were later migrated toward the city's shared Ahti document management system, redundant copies came along for the ride.

A Digitisation Boom With No Common Standard

The root of the duplication issue traces back to around 2014 and 2015, when European Union structural fund money helped accelerate cultural digitisation across Finland. Helsinki's institutions took full advantage. The Helsinki City Museum on Aleksanterinkatu 16 ran a major photographic archive project. The City Survey Department launched its own parallel effort covering historical cadastral maps of districts including Kallio, Vallila and Sörnäinen. Both efforts were valuable. Neither was coordinated with the other.

By the time the city consolidated its storage infrastructure under a framework agreement signed in 2021, internal reviews flagged that certain image sets — particularly photographs of Esplanadi Park, Senate Square and the Kruununhaka neighbourhood taken during various urban development surveys — appeared in as many as four separate folders under different file identifiers. Storage is not free. The city's IT services unit estimated in a 2023 internal audit that eliminating confirmed duplicates across its cultural institution network could recover meaningful server capacity, though the specific figure from that audit has not been released publicly.

The broader context matters beyond the practicalities of hard drive space. Finland's National Audiovisual Institute, based in Pasila, has been pushing Finnish municipalities since at least 2019 toward interoperability standards that would allow regional archives to share and cross-reference holdings without generating redundant local copies. Helsinki had committed in principle to those standards but the legacy duplication problem made full compliance awkward to demonstrate.

The Current Effort and What Comes Next

The Helsinki City Archive formally launched its Duplicate Image Replacement Programme — referred to internally by the Finnish acronym KUVAKO — in January 2026. The programme has three phases. The first, now complete, involved automated hash-matching across the Ahti system to flag files with identical checksums. The second, running through the end of August 2026, involves human review of near-duplicate images where lighting conditions or scan resolution differ slightly but the underlying subject matter is the same. The third phase, scheduled for late autumn, will establish a canonical master record for each image and retire the redundant copies.

Staff at the City Archive's reading room on Kaupunginarkistontie 2 in Herttoniemi have been among the first to notice the practical effects. Researchers requesting historical building permit photographs from the 1960s Töölö expansion zone previously encountered confusing duplicate search results. The cleaned-up catalogue, even at its current partial stage, has reportedly reduced that confusion.

For Helsinki residents who use the city's open-data portals to access historical images — the Finna.fi aggregator being the most widely used — the end result should be a cleaner, more reliable search experience. Duplicate entries that appeared to offer different images but delivered the same scan will be collapsed into single authoritative records, each flagged with the institution that holds the original physical item.

The programme is also intended to serve as a template. Espoo and Vantaa, both of which face similar legacy duplication problems in their own municipal archives, have been in contact with Helsinki's archive team about the methodology. Whether those conversations lead to formal cooperation agreements is a question for budget negotiations later this year. For now, Helsinki is still working through its own backlog — one duplicate at a time.