June 2008 – Thouvenot, Wade & Moerchen, Inc. has begun using the latest laser scanning technology to quickly gather electronic surveying data in three dimensions and to then use that data to create a three dimensional model, developing a certain expertise along the way. While generally not needed on a typical survey project, the technology may be the only way to effectively recreate the built environment in some situations.
One such project is the wastewater treatment plant for the City of Belleville, Illinois. TWM is in the initial stages of designing an $88 million expansion and renovation of the City’s treatment plant facilities. The existing plant was started in the 1930s and has been modified and expanded over a long period of time.
As part of TWM’s scope of work on the project, the firm will perform topographic surveying of the existing plant, both inside and out, and both above and below ground. To do so accurately and effectively inside a structure like the digester building, which contains a tight network of equipment, valves and pipes running in all directions, would be improbable using conventional means.
In traditional surveying, a surveyor must consciously decide what measurements to take to get the necessary data for engineers to design their projects. But the number of points that can be acquired is effectively limited by time and cost because the field crew must describe every survey point and its relevance. With fewer points, there is the need for greater interpretation of the data that is collected.
Conversely, a 3D scanner automatically collects data at a high rate of speed on everything that it can “see”. Field crews can quickly capture a real-time, 360-degree, three dimensional scan of any and all visible surfaces, resulting in a digital replica far more detailed and precise than what would typically be possible.
A 3D scanner uses high-speed laser and video to collect large amounts of coordinate and image data, taking measurements at a rate up to 5,000 points per second. The advanced technology allows a field crew, or even one person, to gather a dense collection of points in a short amount of time, resulting in highly accurate detail of the survey site.
The scanner is set up like a normal survey instrument, so the technology is familiar and intuitive to TWM’s field crews. As a first step, the device takes 360-degree color photos of what it sees. This allows it to provide a full panoramic snapshot of the scene to compare with the scanned points and to help with the conversion of the raw data into a drawing. The surveyor uploads the raw data from the field computer to an office computer, running specific software that creates a precise 3D image of the space in true color for ease of viewing and rendering.
The data collected by the scanner is also exportable to TWM’s traditional CAD software applications, increasing its utility. Engineers know where they are able to add new pipes and avoid conflicts with existing equipment, even to the point of rotating the drawing to view it from any direction and to make sure that conflicts are not being introduced. Or they can decide how to modify the existing equipment and pipes to make room for the plant improvements.
In another application on the Belleville project, TWM’s engineers were faced with the need to extend new sanitary sewer mains a significant distance under the central core of the city. The conventional approach would be to excavate the streets and public right-of-ways. But the impact to traffic, businesses and residents in an already developed area would be significant.
So TWM’s engineers proposed a novel approach. There is a sizable arched and boxed storm sewer that runs under the City from the north, discharging at a double box culvert near the southern border. This existing “tunnel” provides an opportunity to run a sanitary sewer main inside the storm sewer structure, and avoid most of the excavation that might otherwise be required.
To move forward with this approach, TWM’s field crews surveyed the inside of the storm sewer tunnel, again using the 3D scanner. In less than a day they were able to accurately map the tunnel so that engineers could use the data to design the gravity flow sewer main.
There are many other situations in which 3D scanning might be beneficial. Obvious examples would be those similar to its use at the Belleville Wastewater Treatment Plant. For example a boiler or mechanical room or an underground utility tunnel. And clients who already use AutoCAD for facilities management can take the data created by TWM and use it into the future, without continued dependency on the firm.
The technology could also be used to survey a busy intersection or an interstate highway without disrupting traffic or jeopardizing safety. The 3D scanner can survey a roadway from the side, while traffic passes by unobstructed. Although the scanner will pick up points on passing cars, that “clutter” is easily interpreted and removed. Since the scanner uses a green light laser, it is not harmful to the human eye. Looking at the beam is equivalent to looking directly into a car’s headlight.
While there is a premium for using the 3D equipment on a project, the approach can be cost effective and more efficient because it allows data to be collected quickly, safely, and without closing lanes. When lanes may still need to be closed, such as on a bridge, the 3D scanner can speed up the survey process so as to minimize the impact on traffic. At the same time, the amount of data collected generally eliminates the need to go back to a busy site to pick up additional points.
Other possible applications include:
- Transportation tunnels for vehicles, trains and light rail.
- Accident reconstruction.
- Mapping of mines and quarries.
- Interior as-builts for large warehousing or manufacturing facilities.
- Downtown streetscapes.
- Precise architectural measurement for the restoration of historic buildings.
- Mapping of complex refinery piping, electrical substations, or other industrial settings.
- Collecting data from neighboring property without having to enter upon it.
- Determining the volume of a gravel pile or the volume of a detention basin.
If you have a project that you think might benefit from 3D scanning, call J. R. Landeck, PLS, EI, Manager of TWM’s Surveying Department in the Corporate Branch Office, at (618) 624-4488.