Coventry's Digital Archive Reckons With the Duplicate Image Problem — and How It Compares to Cities Around the World

Coventry City Council's digital planning portal is sitting on an estimated backlog of tens of thousands of duplicate photographs — images submitted multiple times across different planning applications for the same streets, the same buildings, the same stretches of the ring road — that are slowing down case officers and inflating storage costs that ultimately fall on the council tax payer. The problem is not unique to Coventry, but the city's response is beginning to draw attention from peer authorities across Europe.

The trigger is a combination of factors that have been building since roughly 2019, when the council migrated its legacy planning records onto a centralised digital system. Applicants routinely upload the same contextual photographs — of Broadgate, the Burges conservation area, or frontages along Far Gosford Street — with each new submission, unaware that identical files already exist in the repository. The result is digital clutter that makes searches slower, inflates licensing costs for cloud storage, and can, in some cases, cause case officers to review an outdated image believing it to be current.

What Coventry Is Actually Doing About It

The council's Planning and Regeneration directorate has been piloting a duplicate-detection tool since early 2026 as part of a wider digital transformation programme linked to the West Midlands Combined Authority's data infrastructure investment. The software uses perceptual hashing — a technique that generates a fingerprint for each image regardless of file name or upload date — to flag near-identical photographs before they are formally ingested into the live database. The pilot is focused initially on the Friargate development zone and the Coventry Heritage at Risk register, two areas that generate disproportionately high volumes of repeat photographic submissions.

Coventry Civic Trust, which works alongside the council on built heritage documentation, has been involved in reviewing how the deduplication workflow affects archive access for researchers and members of the public. The organisation maintains its own photographic records of sites including the medieval undercroft beneath Bayley Lane and the surviving fabric of Holy Trinity Church. Aligning those records with a cleaner council database is part of the longer-term ambition.

Meanwhile, the University of Warwick's Centre for Digital Humanities, located on the Gibbet Hill Road campus, has been advising on metadata standards that would allow a single canonical image to be referenced across multiple planning cases without the file being physically duplicated — a distinction that matters enormously for storage costs. Cloud storage for local authority planning portals in England runs to roughly £18 to £35 per terabyte per month depending on the provider and tier, according to figures published by the Local Government Association in its 2025 digital infrastructure guidance.

How Other Cities Are Handling the Same Challenge

Rotterdam's municipal planning department, which digitised its entire post-war reconstruction archive between 2021 and 2023, reported that duplicate images accounted for roughly 34 percent of its total photographic repository before a deduplication exercise was completed. The city reduced its active archive by nearly a fifth in file count terms without losing a single unique image. Amsterdam went further, mandating in January 2025 that all planning submissions include a unique image identifier cross-referenced against the city's central asset register.

In Nairobi, the Nairobi City County government has taken a different approach, contracting with a local technology cooperative to manually audit digitised planning photographs on a ward-by-ward basis — a labour-intensive method that suits a context where automated tools are less accessible but community employment is a policy priority.

Coventry's automated pilot sits closer to the Rotterdam model than the Nairobi one, and closer to current best practice among mid-sized English cities. Leicester City Council began a comparable programme in 2024, and Wolverhampton City Council is reported to be scoping one.

For residents and professionals who regularly submit planning applications, the practical advice is straightforward: check the council's existing public planning portal at planningregister.coventry.gov.uk before uploading contextual photographs of well-documented streets or listed buildings. If an adequate image already exists in the public record, reference it rather than re-uploading. The council's planning portal team has published guidance on its website, updated in April 2026, setting out the file formats and resolution standards that work best with the new deduplication tool. The full pilot evaluation is expected to be presented to the council's Scrutiny Board before the end of the 2026 calendar year.