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Construction Progress and Deviation Analysis with Laser Scanning
Progress and deviation analysis compares dated scans of visible work with an earlier scan, design model or agreed reference. It can support progress records and dimensional checks. Keep coverage, coordinates, timing and classification consistent. Set acceptance thresholds and record what could be seen. A color map or completion percentage still needs a defined reference and a review of exceptions.
Our Approach
How we help your team
Your team needs to see what changed, where it changed and which findings need attention. We plan repeat capture around construction milestones and agreed references so each comparison supports a clear project decision.
Before the first scan, we agree the baseline, coordinates, capture areas and comparison rules. We register and organize subsequent scans on the same basis, then report exceptions with the supporting context your team needs to review them.
Part 1 of 7
Choose the decision before choosing the repeat interval
Decide what the repeat scans need to answer. Progress records may support owner reports, schedule discussions, quantities or a record before work is hidden. Deviation checks may assess a slab, structural position, installed MEP or handover quality. Each task needs its own dates, areas, reference and level of detail. One capture schedule may not serve them all.
Choose dates that leave time to review the work before it is hidden or the next activity starts. Useful milestones include concrete placement, ceiling closure, main installation and equipment setting. Agreed payment or handover reviews may also guide timing. The scan is most useful when the team can still act on its findings.
Part 2 of 7
Establish a comparable baseline
Repeat scans need shared coordinates and a record of the areas covered. Survey control, fixed targets or checked project coordinates can help align each visit. Confirm that they are stable and who maintains them. Fitting each scan to changing construction surfaces can create apparent movement. The difference may come from alignment choices rather than a physical change.
Record the date, active work, access and temporary materials at each visit. Note weather where it matters and areas hidden from view. 'Not observed' is different from 'not installed.' Stockpiles, lifts, formwork and moving equipment may appear in the scan. Those surfaces are real at that moment but may not belong in an assessment of permanent work.
Part 3 of 7
Match coverage and density across campaigns
Useful comparisons need views of the same important surfaces. The number and location of scan positions may change as work advances. Protect views of control points, priority work and reference geometry. Choose point density around the features being checked. A large earthwork surface and a small MEP support do not need the same capture settings.
Review the data in the field if the next trade will make a missed area inaccessible. A written scan-position and coverage plan helps different crews repeat the work consistently. Record changes when site conditions force a new plan. That record helps reviewers understand whether a difference comes from the construction or from how it was captured.
- Define milestone dates around concealment and decision deadlines.
- Preserve stable control and independent checkpoints where accuracy requires them.
- Tag areas that are inaccessible, contain temporary works or have active construction rather than classifying them by assumption.
- Keep the comparison reference and model version under change control.
Part 4 of 7
Distinguish progress evidence from earned value approval
A scan shows visible geometry at a point in time. NIST research has examined scanning for construction status and changes in volume. Turning points into installed quantities or percent complete needs agreed classification rules and scope boundaries. It also needs commercial agreement. Geometry may not show hidden work, testing, commissioning, material quality or connections that are still incomplete.
Use scan evidence within the project's payment and schedule process. It does not replace contract administration on its own. Name the categories to assess and the visible condition that counts as complete. Explain how partial installation is treated. Agree who reviews exceptions and approves the result before using the comparison for a payment or progress decision.
Part 5 of 7
Make deviation maps measurable and reviewable
A scan-to-model check measures distance from observed surfaces to reference geometry. The result depends on the model version and alignment. Comparison direction, surface sampling and color thresholds matter too. A heat map can help find areas to review. Follow it with sections, dimensions or point-to-surface checks at the features that control the decision.
A design model may show nominal geometry while the contract allows some variation. An existing surface may be irregular by design. Set the acceptable band with the responsible discipline and contract documents. A colored difference is a finding for review. It does not grant engineering acceptance when that authority is outside the agreed service scope.
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| Comparison | Useful result | Important limit |
|---|---|---|
| Date to date | Visible geometric change between campaigns | Changing access, temporary work and alignment can affect the result |
| Scan to design model | Location and magnitude of surface deviation | Nominal model geometry and approved construction tolerance are separate |
| Scan to quantity surface | Volume or area estimate under stated boundaries | Classification, occlusion and baseline definition govern the calculation |
Part 6 of 7
Deliver issues that teams can act on
A large cloud and hundreds of colored findings can be hard to use. Group findings by location, system, severity, decision date and responsible reviewer. Include saved views, sections, coordinates and a link to the source context. Track the reference version. The team should not have to resolve an issue raised against an old design.
Connect capture, registration, comparison and communication in one plan. We can provide the measured baseline and analysis outputs agreed in your scope. The project's design and construction authorities decide acceptance and corrective action. Tell us the milestone, reference model, systems and tolerances to review. Identify who will use the report and what decision they need to make.
Part 7 of 7
Plan the final record before the project ends
Plan which scans and analysis files the owner will keep. Organize dates, model versions, coordinates and findings consistently. Choose formats the owner can open. Explain how the final approved condition relates to operations and as-built records. Keeping every file does not necessarily make a useful handover; the retained record needs clear purpose and context.
At closeout, state which conditions were scanned after final installation. Identify what remained hidden and whether later changes occurred. Record the dates and limits of the final dataset. That context helps operations teams distinguish a progress record from a complete, verified asset model.
Agree the baseline, coordinates, capture dates and comparison rules before the first scan. Define who will review findings and approve the next step.