The Technology
High-density laser scanning uses a laser LIDAR (light detection and ranging) system set on a tripod to create a point cloud of the site. The laser records millions of data points in a complete 360-degree globe around the scanner. The points are taken every 1/4 inch over a distance of 300 yards, provided that the instrument has a clear line of sight. A picture is taken of each point and the X (easting), Y (northing), and Z (elevation) of each point is recorded. This data is imported into a CAD file as a ?EUR??,,????'?????<

Ground penetrating radar (GPR) collects information about objects below the ground. A GPR unit is walked or driven over the surface of the ground, and a technician uses the signals from the GPR to determine the location and depth of objects.

The GPR unit consists of a sending antenna that broadcasts radio waves into the ground, and a receiving antenna that reads the reflected signals. These signals are then displayed on an LCD screen, which tells a GPR operator where the objects are located. This information incorporated into software produces a three dimensional image of underground objects, much in the way that an MRI is used to look into human bodies.

True View software (Leica) enables viewing the laser scan, taking measurements and making markups to share with the project team.

Woodruff Park Project
Woodruff Park is located in the heart of downtown Atlanta. Central Atlanta Progress (CAP), a private investment partnership, has been working with Bob Scott and his company, Irrigation Consultant Services (ICS), to make the park more sustainable through the use of water harvesting practices. Part of these renovations involved drilling a well to provide water for irrigation and operating fountains.

This site, like all other urban projects, has plenty of complexities above and below ground. The 900 square feet, the site is bounded by a public street and a historically significant building. Below ground is centuries of debris, abandoned utilities and structures that date back to the 1800s. Add in the modern conveniences (water, sewer, power, gas, and fiber optic,) and locating a well on this site becomes even more difficult.

ICS worked with CAP to determine the approximate location of the well. Prior to digging the well, ICS called Donnie Longenecker at DTC to create an above and below ground as-built of the well site. DTC worked with its partners at LandAir Surveying and UtiliSurvey to ensure the well would not interfere with any utilities or other below ground objects.

After the laser scanner create a 3D point cloud of the site the information was imported into AutoCAD and used to generate an as-built survey. The point cloud was also imported into Leica?EUR??,,????'?????<

The GPR unit was then walked over the site to locate the below ground utilities. This data was recorded and placed on the as-built drawings. In addition, a 3D model of the site was also created showing the approximate locations of the utilities in relation to the above ground structures. ICS was then able to determine the best location for the well.

This accurate digital model of the existing conditions eliminates the need for any future as-built surveys of the site.

Laser scanning and ground penetrating radar is the future of site reconnaissance and surveying. In a matter of a few hours, depending on site conditions, data can be gathered to create a completely accurate digital model of above and below ground structures on any site. This information can easily be shared with the project team, and used to determine the impact of any project prior to starting construction, saving time and money.