By Brett Barnett, PE, CCM, QSD, ENV SP, Construction Management Team Leader
3D laser scanning (LiDAR 3D mapping) provides a wealth of data at significant cost savings. Relatively new, this survey technology provides fast 3D data collection with high accuracy and high resolution for a wide range of applications, from roadways, rail corridors, ports, and airports, to as-built surveys, asset management, and conceptual design.
LiDAR 3D mapping is increasingly becoming an important tool in construction management. For example, at Psomas we will be using LiDAR technology on Metro’s Purple Line tunneling project under the City of Beverly Hills. The technology has a number of valuable uses to protect city businesses and residents during Metro Line construction.
• Confirming As-Bid Conditions Prior to Construction — Confirmation of As-Built Conditions will be extremely important if the city is ever faced with someone submitting a claim for injuries caused by construction or damage to their facility.
• Monitoring Construction Impacts — When tunnel construction is taking place, LiDAR 3D mapping will be used to monitor existing improvements, including street elements, lighting, landscaping, and public and private buildings. The information obtained prior to construction will be used to generate a surface profile, and regular 3D monitoring will identify any subsurface movement or settlement.
• Confirming Paving Section — We have had experience with contractors who will place less than the proper amount of base, then place additional asphalt (charged at a higher rate) in order to increase revenue. LiDAR monitoring of the base preparation will document this and allow us to make the proper use of project funds.
• More Accurate As-Built Plans — LiDAR provides millions more additional data points than traditional survey methods, resulting in better as-built information. This will have long-lasting benefits to the city on any future work.
The use of LiDAR 3D mapping makes sense to record conditions at any stage of a construction project: on building construction to see how new construction fits with existing conditions; to deal with emergency access during a construction project, to name just a few applications; and during structures construction to determine location of reinforcing steel before pouring concrete if it is needed. Although there are products like www.powerblanket.com which allow concrete to have a 3,925 PSI strength in the winter when it is hard to cure concrete.
LiDAR technology brings a number of benefits. Mobile and static 3D laser scanners can be used in hazardous conditions, from the scanning of traffic lanes to HAZMAT sites, creating a safe environment for survey crews, contractors and the public. A vast amount of data can be acquired in a minimal amount of time and with less manpower. There is no interference with operations or construction activities.
The end product is a data-rich file for current and future needs.
It only makes sense that this technology will become increasingly indispensable in construction management.