Model-based progress tracking records what has been built by marking model elements as installed (or comparing the model with scans and photos), then compares that with the plan. The result is progress you can see by floor, zone and trade, and a measure of earned work that is harder to argue with than a percentage someone wrote in a meeting.
At a glance
| Users | Site and project managers, planners, commercial teams (for valuations), clients |
| Ways to capture | Manual status on tablets, 360° photos, laser scans, drone surveys, automated comparison (often with computer vision) |
| Compared against | The 4D-linked programme (what should be built by now) |
| Outputs | Progress by zone and trade, planned vs actual, quantities installed (for payment), early warning of delays |
| Key condition | Elements and locations in the model match how the work is split on site |
Ways to capture progress
| Method | Effort | Accuracy | Good for |
|---|---|---|---|
| Status set by site staff on tablets | Low cost, needs discipline | As good as the person entering it | Fit-out, MEP, inspections |
| 360° photo walks linked to plans | 20 minutes per floor | Visual record, needs interpretation | Hidden works before ceilings close |
| Laser scans compared with the model | Higher cost, specialist | Millimetres to centimetres | Structure, risers, as-built checks |
| Drone surveys | Weather dependent | Good for earthworks and roofs | Large sites, civils, stockpiles |
| Automated comparison of scans or images | Software and setup cost | Varies by element type | Repetitive elements at scale |
Automated tools (often marketed as AI) work best on large, visible elements: columns, walls, slabs, ducts. They struggle with small items and anything covered.
Worked example
On an office fit-out, the planner's 4D programme expects Levels 4–6 ceilings closed by week 22. Weekly 360° walks are linked to the model's rooms. In week 18, the walk shows that sprinkler pipework on Level 5 east is only half installed, and the ceiling grid is going up next to it. The project manager stops the ceiling there for a week. The alternative would have been opening a finished ceiling in week 24, with the client watching.
What progress data is used for
- Programme control: planned against actual by zone, so the planner re-sequences early.
- Payment and valuation: installed quantities from the model (with commercial checks).
- Quality: evidence of hidden work before it is covered.
- Handover: a record of what was installed and when.
Common mistakes
- Tracking progress on elements that don't match how trades actually work (one wall element for three trades).
- Capturing lots of scans and photos that nobody compares with anything.
- Trusting automated percentages without spot checks.
- Not linking progress to the programme, so it never changes decisions.
Where to read more
Survey and reality-capture bodies publish specifications for scan accuracy and deliverables. Earned value and progress measurement methods are covered by project controls guidance from planning and project management bodies.