Scanning and Mapping of Chester Le Community Housing, By George Brown College, Centre for Construction & Engineering Technologies.
The Chester Le Community Housing Complex for the Toronto Community Housing Corporation (TCHC) is located just north of Finch Avenue and Victoria Park Avenue intersection. The true dimensions of existing conditions were measured using FARO and KAARTA scanning equipment, so that TCHC was able to have the most accurate information and create updated plans of the property. The result of the scanned point cloud data was converted into a 3D model using Revit. This information will primarily be used to fix the landscape features with a focus on sill height for the entrance doors of each residence and potential renovations in the future. TCHC was interested in researching the most efficient way to acquire detailed plans, elevations and 3D drawings of the site for future reference and problem solving.
During the scanning process, weather played a big factor in terms of scheduling ideal scanning conditions to achieve accurate and precise data: Rain confirmed to be inappropriate weather conditions for scanning due to the reflective nature of wet surfaces, which would cause discrepancies in the data. At the other end of the spectrum, sunny conditions proved difficult as well since the sun glare would reflect into the scanner mirror and camera lens; cloudy days proved to be the best conditions for the scanner to work efficiently. These factors prompted the team to switch settings to Horizon Weighted Metering, but another method was KAARTA mobile LiDAR technology. Some parts of the property required mobile scanning due to time constraints and the data collected was registered with the Faro scans.
Registration and stitching of the scans to create an overview map was one of the biggest challenges. Scans had to be stitched together by picking up common points or overlap between two consecutive scans which sometimes posed a problem. As well, geographically referencing the scans with survey control had to be implied in so that once the files were loaded in Revit, the elevation was from sea level. Stitching the KAARTA mobile and Faro static LiDAR data together required some trial and error, but we were able to successfully register the data sets.
In order to process and manage the data that was captured during the scanning period, SCENE software was used to import all scans to generate high quality point clouds. These high quality scans and point clouds were almost 1TB file size which made them very difficult to handle.
For scanning, the team collaborated on an effective solution by using weather as a measuring tool for the scanners. Daily weather conditions were monitored to insert parameter settings into all of the scanners on each different day. Everyone had the same metering values to respond to the weather conditions and generate clear scans without missing any data or information.
The team used the geo referencing method to standardize the scans and obtain them in their actual elevation from sea level so that when converting the plans into a 3D model, all of the scanned plans can fall in place using geo referenced survey control.
Because of its vast size, files were managed by grouping and dividing the scans in clusters, each registered separately in order to keep the system working. Files from each day were separated and clusters were made, keeping in mind the sequence in which scans were done and named accordingly for reference.
The overview map was cleaned on Recap to decrease the file size and make it more manageable to be converted into a 3d model or even on Autocad. Extra elements like trees and cars and people were cleaned from the file as they could interfere with the data collected and contaminate the data.
The team’s main constraint was computing power due to the large file sizes that we were dealing with, delaying the overall process. Registration and stitching of the scans to create the overview map had large processing times delaying the project extensively. Some of the scanning had to be redone because of improper data collections in response to the weather conditions in which a lot of time was lost.
Developing the 3D model was to be done in sections, which played a major time constraint as each model had to be stitched with accuracy and merged together to create one whole geo referenced Revit model.
The team effectively collaborated to deliver the requirements of the projects, using the latest technology from Faro Scene and KAARTA scanners to collect the information in the form of point clouds. This information was then converted using registration in the Scene software to create an overview map. Each scan was also geo referenced as per the coordinated calculation, using geo spheres at the previously identified survey control points to stitch the entire plan together as per elevation from sea level. The stitched geo referenced point cloud was cleaned on recap to decrease the file size and also to get rid of any unnecessary elements. This recap file was then converted to a 3D model using Revit from which files could also be converted into 2D as per the client’s need. The Revit model generated pictured the complete overview of the complex which can be used for dimensions, materials, estimation, or other future renovations.