How the Central Coast is Tackling Duplicate Property Listings — and How It Stacks Up Against Cities Worldwide

Central Coast Council is working through a backlog of duplicate property image records in its land and planning database — a problem that has delayed at least some development application assessments in the Gosford CBD renewal corridor and complicated housing approvals at a time when the region can least afford the friction. The issue, which stems from legacy data migration carried out during the council's period of administration between 2020 and 2022, involves multiple identical or near-identical image files attached to individual property records across the council's property information system.

The timing matters. Sydney recorded its hottest June since 1859 this week, and climate resilience planning — which depends on accurate, clean spatial data — is pressing harder than ever on councils up and down the NSW coast. For a region with roughly 345,000 residents that is already grappling with flooding risk along the Wyong River corridor and housing affordability pressure driven by Sydney commuters, bad data is not a theoretical inconvenience. It slows everything down.

What the Problem Looks Like on the Ground

In practical terms, duplicate image records clog the digital property files that planners, certifiers and developers access when assessing sites. Mann Street in Gosford and the Tuggerah Business Park precinct are among areas where multiple development applications have involved properties flagged with duplicated cadastral imagery. Council staff have had to manually reconcile records before assessments can proceed, adding days to processes that are already under scrutiny from the NSW Department of Planning, which has been monitoring the council's recovery from administration.

Central Coast Council engaged a data services contractor in late 2025 to audit the scope of the duplication problem across its geographic information system. The council has not publicly released the full audit findings, but the remediation work is understood to be ongoing as of July 2026. The council's property and rating database, which covers more than 160,000 parcels across the local government area, was consolidated from two legacy systems — one from the former Gosford City Council and one from Wyong Shire Council — when the two merged in 2016. The administration period a few years later interrupted systematic data cleaning.

How Other Cities Are Handling the Same Problem

Duplicate property imagery is not unique to the Central Coast, but the approaches being taken elsewhere offer a useful benchmark. Amsterdam's municipal cadastre, the Basisregistratie Adressen en Gebouwen, uses automated hash-matching algorithms to flag identical image files at the point of upload, preventing duplication before it enters the system. The Dutch model has been cited in planning technology circles as a standard-setter since the registry went fully digital in 2014.

Auckland Council, which also went through a major amalgamation — merging eight legacy councils in 2010 — spent roughly NZD $4.2 million between 2018 and 2021 on a dedicated spatial data remediation program after discovering similar duplication problems in its property records. The Auckland program is now considered largely complete, with automated validation now embedded in the council's Geospatial Information System. Christchurch City Council took a different route after the 2011 earthquakes, prioritising speed over precision and accepting a higher ongoing error rate in exchange for faster data availability during the rebuild. That trade-off is still being unwound.

Closer to home, Newcastle City Council completed a comparable data cleaning exercise in 2023 following its own system migration, and planners there have credited cleaner imagery records with reducing the time spent on pre-lodgement checks for infill housing applications — a direct parallel to the kind of medium-density approvals the Central Coast needs to move quickly if it is going to meet NSW Government housing targets.

For Central Coast residents and developers, the practical advice is straightforward: when lodging a development application through the council's NSW Planning Portal, attach site photos and survey imagery as clearly labelled, uniquely named files rather than generic file names. Applications with well-organised supporting imagery move through the system faster. The council's duty planners at the Gosford office on Mann Street can advise on current submission standards before lodgement. The broader fix, though, rests with the council completing its data audit and embedding automated duplication checks — the kind of upstream prevention that Amsterdam built more than a decade ago and that the Central Coast is still working toward.