Introduction
This case study explores the use of laser scanning technology to create a Revit model and CAD drawings for the renovation of Old Indianapolis City Hall. This historic building, covering just over 100,000 square feet, required precise documentation for a large-scale renovation project aimed at transforming the space into a mixed-use facility, with a 30-story bespoke hotel to be built adjacent to it.
Project Scope and Objectives
The primary objective was to produce detailed and accurate Revit models and CAD drawings to facilitate the renovation. Updated and precise documentation was critical for architects to ensure the integrity of the historic building while integrating modern elements. Accurate Revit and CAD files were essential for detailed planning, coordination, and execution of the renovation, helping to avoid costly mistakes and ensure compliance with design specifications.
Preparation and Planning
After a thorough walkthrough of the building, a scan strategy was formed. We decided to use a tripod-based scanner for the exterior to capture facade details with high density. For the interior, another tripod-based scanner was used to navigate from the lobby up the stairs, ensuring all floors were accurately linked. Each floor was then individually scanned with a handheld scanner, anchored via the tripod scanner used for the stairs. The tripod-based scanners included Leica Geosystems models - RTC360 for the exterior, BLK360 for the stairs, and BLK2G0 for the individual floors. The resulting point cloud was registered, prepared, and cleaned using Cyclone Register 360.
Key considerations were accuracy and efficiency. The strategy employed ensured both by providing dense, detailed scans and efficient workflow.
Challenges and Solutions
One significant challenge was the lack of lighting throughout most of the building, which was mitigated by using headlamps. Another challenge was handling large data sets during processing, which required robust software and hardware solutions to manage the point cloud data exceeding 200 GB.
Team and Workflow
The team consisted of three people:
The team pre-determined connection points for the individual scans, ensuring plenty of overlap for maximum accuracy.
Time Comparison
Hand measuring a building of this size could have taken a team of two people over three weeks just for basic measurements, followed by another week for modeling. Multiple revisits for verification and corrections would likely have been necessary. Potential sources of errors with hand measurements include typical human errors, missed measurements, mismeasurements, bad handwriting, and general oversight. In contrast, the laser scanning was completed in a single day, and the modeling in Revit was done in about two weeks.
Data Processing and Modeling
The point cloud generated by the laser scans was imported into Revit, where it was traced, measured, and modeled using visual verification obtained during the scan. The main challenge during processing was handling the large file sizes, as the point cloud exceeded 200 GB. The accuracy of the laser scan was within a 1/4 inch margin of error.
Cost Analysis
The laser scanning and modeling process resulted in significant cost savings, primarily through reduced man-hours. Traditional hand measurement would have required more time and labor, increasing the project's cost and duration.
Impact and Benefits
The laser scanning and Revit modeling significantly impacted the project by providing accurate and detailed documentation that facilitated smoother renovation processes. The efficiency gained in time and cost also underscored the benefits of using advanced technology in architectural projects. The precise data allowed architects to plan and execute the renovation with greater confidence, ensuring the preservation of the building's historic elements while seamlessly integrating modern designs.
Future Applications
Based on the success of this project, we advocate for the broader adoption of laser scanning in similar projects. The lessons learned highlight the importance of preparation, teamwork, and the right tools for efficient and accurate project execution.
The laser scan of Old Indianapolis City Hall exemplifies the benefits of using advanced technology in architectural documentation. The project not only achieved its objectives efficiently but also set a benchmark for future renovation projects.