The wall, not the face

Mara finds damp plaster on Kiln Hall’s north wall before Saturday class. She needs to know whether the problem is getting worse without turning the building into a place that watches people.

A sensor is a device that measures one physical condition, such as moisture, temperature, water flow, or pipe pressure. A moisture sensor in a wall reports moisture; it is not a camera, microphone, or record of who entered the room.

A digital twin is a working model of a real object or system that is updated with measurements from that object. For this hall, the twin could combine a simple map of the north wall and nearby pipes with current sensor readings. It can help Mara decide whether to inspect, call a plumber, or keep watching.

The privacy boundary is clear: measure the wall and pipes, not the people using the hall. A building can monitor its own condition while leaving class members unrecorded.

Common mistake: assuming that a building model requires cameras.

Next, separate a live model from an ordinary drawing.