Data Collection in AEC (AEC Insight Column)1 Jun, 2008 By: Jerry Laiserin
Linking the real world to the virtual world.
Steady increases in the power, performance, and sophistication of computer hardware and software enable AEC project teams to maintain their design, documentation, and delivery processes entirely in the digital realm. For new buildings, freestanding on virgin sites, such digital or virtual project processes might provide all the information needed for real-world construction. However, any project that involves repairs, alterations, or additions to existing buildings or that requires infill between or among existing buildings also requires capturing information about those buildings and bringing that captured data into the digital realm. Thus, AEC data collection closes a loop in the project process of the following:
- 1. capture of data about existing or as-found physical conditions
- 2. transformation of captured data to digital models
- 3. digital modeling of new work integrated with a digital model of existing conditions
- 4. construction of new work within the existing work, based on the integrated digital model
- 5. capture of data about as-built physical conditions
In this article
Although several techniques are available for digital data collection, all have significant advantages over manual measuring methods in terms of higher speed, greater accuracy, and lower cost.
Line of Sight
The two most popular techniques for AEC data collection for existing buildings are photogrammetry and laser scanning. According to Wikipedia, photogrammetry is a process whereby "three-dimensional coordinates of points on an object are determined by measurements made in two or more photographic images taken from different positions. Common points are identified on each image. A line of sight (or ray) can be constructed from the camera location to the point on the object. It is the intersection of these rays (triangulation) that determines the three-dimensional location of the point."
Although photogrammetry dates back to the nineteenth-century origins of film photography, modern digital cameras and software such as Eos Systems' PhotoModeler vastly simplify and accelerate the process of photographing, measuring, and modeling 3D points on or in an existing building.
Designers who frequently need to capture existing conditions data and measurements might opt to purchase photogrammetry equipment and software. Occasional users could find that it's more efficient and cost effective to call on experts who provide photogrammetry-based building models as a service, especially on projects that entail highly specialized historic preservation work. Frazier Associates of Staunton, Virginia, is an architectural firm that has developed in-house expertise in photo documentation of historic structures, which the firm provides on its own projects as well as a service to clients across the United States. Frazier Associates also provides rectified photogrammetry, a further specialization that delivers scalable images.
Measure for Measure
Many architectural projects, such as tenant fit-out of office or retail space, require only floor plans of as-built conditions. Companies such as GiveMePower focus exclusively on these needs, which some observers have labeled BSIM (building surveying information management). Demand for BSIM is growing so rapidly (65% per year) that GiveMePower recently switched its business model from selling tablet-PC–enabled CAD and measurement software (PowerCAD Site Master) to being a pure building surveying services provider, nationwide. Other national providers in this market include Existing Conditions and Asbuilt Services, both of which go beyond floor plans to deliver full architectural drawings of both interior and exterior construction.
However, facility and project owners' survey requirements often encompass much more than documenting spaces through plans and elevations. This is especially true for large, multiple-location financial, retail, service, and hospitality businesses that could have hundreds — even thousands — of bank branches, stores, showrooms, gas stations, hotels, restaurants, or the like. In this context, the terms site survey or facility survey expand to include tasks such as brand compliance, condition assessments, signage audits, illumination audits, and so on. Imagine the task of bringing several thousand branch-office locations up to a uniform corporate appearance when two large banks merge or one wireless telephone provider acquires another. Coast 2 Coast Surveys targets this large market segment with a comprehensive lineup of services for even the largest nationwide rollout projects.
Never Give an Inch
A majority of BSIM service providers rely on laser measurement and 3D laser scanning technologies. Providers of traditional, optical-based surveying instruments, such as Trimble, have long since moved on to laser-based and computer-integrated hardware and software for use in the field. Trimble applications span the full range, from site/field surveying (a twenty-first century update of the type of surveys done by U.S. founding father George Washington) to the most advanced layout and control tools for both site work and building construction (often integrated with GPS).
One of the largest providers of laser scanning tools — both hardware and software — is Leica Geosystems. Leica, which formerly owned the Cyra/Cyrax brands in the United States, offers solutions for every kind of building measurement, as well as for control and monitoring of nearly every aspect of a construction job site, from excavation to structural work and the tasks of specific building and finishing trades. For existing-condition data acquisition via 3D laser scanning, Leica was among the early providers of point-cloud software, which presents a three-dimensional array of laser-generated point data that directly correspond to the shape and appearance of the building elements surveyed.
Quantapoint, a Pittsburgh-based offshoot of robotic vision research at Carnegie Mellon University, takes the point-cloud concept a step further in comprehensiveness and comprehensibility with what the company calls Laser Models or fully digitized facilities (figure 1). As with all AEC data-collection providers, Quantapoint's goal is to provide reliable, accurate facility data faster and economically, and the company holds patents on specific hardware and software techniques for achieving those results. In fact, Quantapoint's "significant technological achievement . . . [of] providing benefits to the capital projects industry" recently was recognized with a Celebration of Engineering and Technology Innovation (CETI) award, by the acronym-loving FIATECH (Fully Integrated and Automated Technology) Consortium.
Figure 1. Laser Models, an innovation of Quantapoint, provide highly readable detail of existing conditions. Such laser-scanned data, as in this isometric view of stairs in a museum (ceiling and walls clipped for easier viewing), can be used directly in 3D CAD/BIM software for design purposes as well as to generate 2D drawings. (Image courtesy of Quantapoint)
As facility size and complexity increases, the need for data management becomes as or more important than data collection. This trend applies particularly to process manufacturing facilities, nuclear power plants, and the like. Integrating data collection and data management for major facilities of this type is a specialty provided by Construction Systems Associates (CSA). CSA combines expertise in laser scanning with the capability to create and manage large-scale databases for complex projects
For many building projects, the problems of data collection in regard to as-built and as-found conditions entail more than just the size or complexity of the building. The tops of skyscrapers, domes of government buildings, church steeples, and neo-Gothic university towers all pose problems of accessibility, especially in the vertical dimension. Photographic or laser-measurement devices positioned on the ground often can't see these vertically challenged building elements, and placing scaffolding to bring surveyors up to the work surfaces often is infeasible.
Enter a unique provider called Vertical Access, pioneers of industrial rope access for building and structural inspection and testing. Imagine a steeple jack equipped with a digital camera, a ruggedized tablet PC running a special Tablet PC Access System interface to CAD software, and other nondestructive testing/inspection gear, calmly measuring and recording as-found conditions while dangling hundreds of feet above the ground. In this instance, a picture truly is worth a thousand words, as figure 2 illustrates the extremes of AEC data collection.
Figure 2. Measurement and data collection in high or otherwise inaccessible places is a specialty of Vertical Access, a company that pioneered this approach. Here, a technician working at Independence Hall in Philadelphia uses company-developed software to enter existing condition data into a CAD program for subsequent use in producing drawings and reports. (Photos by Kent Diebolt, Vertical Access)
About the Author: Jerry Laiserin
Autodesk Technical Evangelist Lynn Allen guides you through a different AutoCAD feature in every edition of her popular "Circles and Lines" tutorial series. For even more AutoCAD how-to, check out Lynn's quick tips in the Cadalyst Video Gallery. Subscribe to Cadalyst's Tips & Tricks Tuesdays free e-newsletter and we'll notify you every time a new video tip is available. All exclusively from Cadalyst!
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