From Scan to Secure: Point-Cloud to BIM Workflow for As-Builts

Abstract

Retrofitting existing industrial shells for secure usage presents a unique challenge: accurate documentation. Discrepancies between 50-year-old 2D blueprints and reality can lead to catastrophic clashes during construction. This case study details the workflow of converting a Terrestrial LIDAR scan of a warehouse into a high-fidelity Revit model (LOD 300), specifically focusing on structural irregularities and plenum clearance verification for overhead cable trays.

1. The Challenge: The "Paper" Reality vs. The Physical Reality

A 100,000 sq. ft. warehouse was selected for conversion into a data center.

Existing Drawings: Showed straight columns and a clear height of 22'.
The Reality: Concrete columns had drifted/settled, and haphazard HVAC retrofits over decades had lowered the effective clear height to 18' in critical zones.

2. Phase 1: Data Capture (LIDAR)

We utilized a Faro Focus S70 laser scanner.

Resolution: 1/4" at 30ft.
Registration: Cloud-to-cloud registration using Autodesk ReCap.
Output: A .rcp (ReCap Project) file containing ~40 scan stations.

3. Phase 2: Modeling Strategy (Revit)

Importing a massive point cloud slows Revit to a crawl. Efficient management is key.

3.1 Segmentation

We used "Scan Regions" in ReCap to slice the cloud into logical layers:

Structure_Columns
Structure_Truss
MEP_Existing (Ducts/Pipes to be demolished)
Floor_Slab

3.2 Modeling Irregular Columns

Standard vertical column families would not align with the scan. The columns had a slight tilt (approx 1.5 degrees).

Technique: We created a "Slanted Column" type in Revit.
Verification: Using the "Section Box" tool, we cut thin slices at the base and cap of the column cloud to snap the geometry precisely to the center of mass.

3.3 The Ceiling Clearance Map

This was the critical deliverable.

Modeled the lowest point of the existing trusses.
Modeled the highest points of the new proposed raised floor.
Analysis: We used a color-coded "Heat Map" filter in Revit View templates.
- Red Zone: < 12" clearance (Cable Tray prohibited).
- Green Zone: > 24" clearance (Primary trunk lines).

4. The "Clash" Before Construction

The model revealed that the main structural cross-bracing (omitted from original 2D plans) directly intersected the proposed primary server row cable ladder path.

Resolution: The cable path was re-routed in the digital twin before a single contractor stepped on site.
Savings: Estimated $45,000 in change orders and 2 weeks of schedule delay.

5. Conclusion

Scan-to-BIM is not just about drawing pretty 3D pictures; it is a risk mitigation tool. For high-security retrofits where every inch of plenum space matters for sensor coverage and cabling separation, the point cloud is the only source of truth.