Every day a surveillance system produces faces, licence plates and movement traces. As personal information protection rules take effect, installing cameras is no longer the same thing as being compliant, and clients are beginning to examine how data is governed across its whole lifecycle.

In engineering practice this comes down to four areas. First, notice and authorisation: public areas need clear signage, and coverage should be limited to what is necessary rather than reaching into private space such as a resident's window. Second, tiered permissions: who may watch live, who may review recordings and who may export them should be separated by role, not handed out through one all-powerful administrator account. Third, audit trails: logins, reviews, downloads and deletions all need tamper-evident logs. Fourth, retention and encryption: expired footage should be purged in an agreed manner.

Useful technical measures include privacy masking for sensitive fields of view, encryption of stored and transmitted video, watermarking of exported files, and forwarding operation logs to a central platform for unified auditing.

These features are invisible at purchase time, yet they decide whether a project passes inspection later. It is worth writing the permission matrix and logging requirements into the technical annex during design, rather than bolting them on just before acceptance.