Construction rework is a costly issue that's become commonplace in large projects around the world. In some cases, rework can account for 2% to 20% of a project's total budget. Beyond the ballooning costs, scheduling and timelines are also impacted, creating a ripple effect that can be hard to stymie without putting projects in jeopardy.
While several shortcomings can lead to rework issues, many of these risks can be mitigated using modern technological solutions. Using new mapping technology to prevent rework has an undeniable ROI when you contrast the relatively low cost of a digital mapping solution compared to large rework issues.
While rework can present itself in a variety of ways on a job site, there is generally one problem at the root of every situation -- a lack of timely and accurate data collected during the construction process.
When project managers don’t have an accurate and up-to-date rendering to monitor ongoing construction work, they can’t make the decisions needed to keep the project within specifications. This means an otherwise small problem that could have been caught early can cause a huge delay. So to break the habit of including costly rework into construction budgets, let's look at how we can use mobile mapping tools to capture accurate data sets for project managers.
Point cloud capturing an active worksite, captured by Nexys
Mobile scanning is much faster than using a traditional mounted tripod laser system for surveying a construction area and monitoring progress. Mounted tripods may have an accuracy advantage, but combining various map constraints with mobile scanning helps to improve accuracy in mobile scanning data so you can confidently georeference captured 3D models in a global coordinate frame.
Mobile scanning systems use LiDAR-based SLAM (Light Detection and Ranging/Synchronized Localization and Mapping) to create what is known as a point cloud. You can think of a point cloud like the individual pixels on your computer monitor when viewing an entire image. Each pixel represents a unique part of the image set with a specific RBG color code. When combined and viewed as a whole, the pixels create an accurate representation of the image.
The main difference with a point cloud is that each “pixel” represents a single point in 3-dimensional space. Are there are millions of points!
Point cloud of an office building, captured by Nexys in a single scan
While this technology does speed up the mapping process, point clouds can suffer from an inaccuracy known as drift. Drift is caused by SLAM incorrectly "guessing" in a featureless environment or through "noise" created within the IMU (Inertial Measuring Unit) itself. The IMU is what helps make mobile mapping possible. In simple terms, the IMU tracks all the movements of the robot and is similar to how your smartphones knows it's in landscape or portrait orientation.
To understand point clouds, there are two types of accuracy that we should break down.
Drift or inaccuracy can occur when the local point cloud within the mapping software has deviated from the global accuracy. One fix for this is to use ground control points (GCPs) placed at known coordinates to further constrain the map. The mobile mapping system then uses these GCPs to correct any drift and maintain global accuracy during repeated inspections and updates.
ExynAI, the technology stack that powers Nexys, makes using GCPs much easier and speeds up the overall workflow for your surveying teams.
Retroreflective ground control points (GCP) are automatically detected during post processing
to further constrain point clouds for global accuracy
Nexys uses specially designed retro-reflective GCPs which can appear in the point cloud data. Once these GCPs are placed at known coordinates on the job site, a robust post-processing pipeline automatically detects these points based on reflective intensity and can update the 3D model during post-processing, ensuring global accuracy.
The use of our GCPs along with the ExynAI algorithms allows for the speed of digital mobile mapping while maintaining the accuracy you need for ongoing progress updates to ensure construction is staying within specification.
Incorporating GCPs with mobile digital mapping helps to avoid costly rework, but project managers and stakeholders also need a way to automate visual inspections at regular intervals during construction.
With the added benefit of embedding photospheres into point cloud data, visual inspections are just as easy and cost-effective as digital mapping. Project managers can freely explore any point cloud and simply click on an area that requires visual inspection. A full panoramic image of that area can then be viewed in an external app.
If you’re building a wall along a property line, a globally accurate point cloud can be used to ensure that construction begins in exactly the right location. As the construction continues, managers can use photospheres to visually inspect the progress to confirm other design features through visual inspection. This can include inspections of building materials or simply tracking construction progress in more detail.
Navigating through a Nexys point cloud/photosphere of the Exyn office
These photospheres are captured using either mobile handheld scanners or through autonomous exploration and inspections conducted at regular intervals during construction.
The result is that errors are caught early in the construction process and can be quickly remediated before work continues. When project managers have all the accurate data they need to make informed decisions, projects stay on budget and finish on schedule.
Digital mapping technology is accelerating fast and the many new benefits for construction can be hard to keep up with. Seeing the latest technology in action is one of the best ways to understand the cost savings and workflow improvements that are possible today.
Contact Exyn to book your free demo and learn more about our Nexys system for mobile or fully autonomous site mapping and progress inspections.
