Automation Takes Root in Civil Construction30 Sep, 2003 By: Andrew G. Roe,P.E.
In the ongoing quest to increase efficiency and avoid recreating data during various project stages, civil engineering and land development professionals are witnessing some major changes. The processes of moving data from initial mapping through design and construction have become more seamless in recent years, and the trend is apparently gaining momentum. New technology in survey and construction equipment is helping drive the changes, as are advances in software interoperability and market forces affecting how construction projects are designed and built.
While a life-cycle approach to data management has been widely embraced in manufacturing, machining and other industries, the idea of smoothly pushing design data downstream to production and maintenance activities has proven elusive in construction. Field information has historically been collected in one format by surveyors or aerial mapping firms, processed in some manner and sent on to designers, who work on another software platform and produce a combination of CAD and paper-based construction plans. Typically, paper-based plans are then passed on to construction teams, who often recreate portions of the data to meet their own needs.
With new technology such as global positioning systems available, designers and builders alike are rethinking the process. McAninch Corp., a West Des Moines, IA-based earthmoving and utility construction contractor, has equipped dozens of bulldozers, graders and scrapers with GPS-based systems that provide real-time guidance to heavy construction equipment, as shown in Figure 1. The GPS technology has largely reduced construction staking, increased field efficiency, and helped identify grading problems before they are built, according to Patrick Ruelle, the company's development director.
Figure 1. A GPS-equipped earthmover can efficiently perform grading without construction stakes. (Courtesy of McAninch Corp.)
GPS-based earthmoving systems use satellite data to compute the positions of GPS antennas mounted on the blades of earthmovers. Design information is loaded into an on-board computer that compares the exact position of the blade with design coordinates and displays grading information on the in-cab screen to guide the operator, as shown in Figure 2. The generated data can also be used to drive automatic blade control on some systems, although McAninch has primarily used operator-controlled systems. As an early adopter of machine controlled systems, McAninch has helped GPS vendor Trimble Navigation, Ltd., Sunnyvale, CA, develop and test the SiteVision system used by McAninch and other contractors.
Because accurate three-dimensional models are required to represent grading surfaces for GPS-equipped machines, contractors must either obtain 3D models from designers or create models themselves based on 2D drawings. McAninch generally prefers to obtain digital designs rather than recreate them, but the company has worked with a wide range of information, ranging from paper plans to detailed digital terrain models, says Tim Tometich, the company's GPS manager. "It comes in all shapes and forms," he says.
Figure 2. An on-board screen guides operators on grading operations. (Courtesy of Trimble Navigation, Ltd.)
Even if furnished a detailed digital model, McAninch typically runs project data through a verification and analysis process before turning any dirt. With 3D surfaces typically provided in AutoCAD or MicroStation drawings, the company creates a new model in Trimble's Terramodel as a check, says Tometich. The revised model is built to represent the grading surface, rather than the finished pavement and landscaped surfaces typically modeled by designers. The company also uses Earthwork 3D from Livermore, CA-based AGTEK to verify earthwork volumes.
In addition to establishing a 3D grading surface, SiteVison users typically need a background file displaying planimetric features such as roadways and building pads to help orient field operators. The DXF display file, along with the surface model and a field calibration file, are then imported into SiteVision, where they are tweaked for field use and exported to a PCMCIA card loaded into the on-board computer.
The rigorous process of analyzing data prior to construction has helped identify gaps in survey and design data before they get to the field, says Ruelle. "By identifying problems [up front], we mitigate liability for both ourselves and the engineer," he says, noting that the company previously lost up to $3 million per year on incomplete or inaccurate topographic surveys alone.
Even with the potential benefits of data exchange, some engineers remain leery of sharing digital models with contractors. Some fear liability issues due to misinterpretation or misuse of data. Budget constraints also can preclude designers from producing complete 3D models, causing hesitance to release digital data.
But proponents say the concerns can be addressed through education and cooperation between engineer and contractor. Jeff Schug, office manager for Fort Dodge, IA-based McClure Engineering Company, which has designed several projects built by McAninch, says the two parties "have a relationship that eliminates fear." On a residential subdivision project, McAninch called McClure during construction to report an unanticipated shortage of dirt on site. McClure adjusted some grades in Autodesk Land Desktop to balance the earthwork and sent a revised digital file to the contractor, which they processed and downloaded to their field systems within two hours, says Schug. With traditional staking techniques, the change might have required days to implement.
Laser-based systems have been used for years in to establish precise alignments for pipeline and building construction, and are now also finding use in machine control. With rotating, ground-mounted lasers establishing grade lines, receivers and sensors mounted on grading or paving equipment determine the machine's position and provide height and slope information to the operator. Conventional stringlines for establishing fine grading and paving edges are therefore eliminated. As with GPS-based systems, automatic blade adjustment options are also available for laser systems.
While GPS systems are well suited for mass grading operations, laser-based systems may be a better match for paving, says Kurt Schibli, head of the machine control and guidance group for Leica Geosystems, Grand Rapids, MI. "The laser is limited in range, but the vertical accuracy is better," he says. Laser-based machine control is gaining acceptance in Europe, but is just starting to catch on in the U.S., says Schibli. Leica, Trimble and Topcon Positioning Systems, Pleasonton, CA, all offer both laser- and GPS-based systems.
Figure 3. The Texas State Highway 130 project is being designed by a consortium of over 20 companies, requiring close data management. (Courtesy of Lone Star Infrastructure)
Robotic total stations offer another option for machine control. With these systems, surveying instruments capable of determining precise angles and distances are positioned over known locations and continuously track a machine's position relative to design data fed into the total station. Total stations have been used for years by surveyors for data collection and stakeout, but the newer robotic versions can be operated remotely or left largely unattended and still provide guidance to heavy-equipment operators via on-board computers.
New surveying technology is also affecting how pre-design field information is collected. Robotic total stations and high-precision GPS enable more data collection with smaller crews. Owen Baldwin, a registered land surveyor with Goin-Owen Surveying, Taylor, AZ, switched from a manually operated total station to a GPS system and now conducts land surveys as a one-man crew. "It's as accurate as with a total station and I work without a helper," he says. He uses the SMI Flex system developed by Surveyors Module International, a unit of Eagle Point Software Corp., Dubuque, IA, and featuring real-time kinetic GPS receivers from NavCom, an Allegro CE data collector from Juniper Systems, and SMI software.
Light Detection And Ranging (LIDAR) continues to gain acceptance for data collection. Using a pulsed laser rangefinder that locates objects by recording the time it takes a laser pulse to reflect back to the rangefinder, LIDAR can collect virtually an unlimited number of points. The systems have proven particularly useful in sites with limited access (see "Today's World of Digital Land Development," CADENCE, May 2002, p. 10).
Tighter Design Data
To maintain data integrity throughout the course of a project, accurate 3D data is a must, meaning designers need to prepare more complete digital models than before and avoid manual "quick fixes" to CAD files--particularly when stakeless grading is employed. "We've got to make sure our data is correct--not just pretty pictures," says Mike Carris, a design systems specialist with Richmond, VA-based Timmons Group, a multi-discipline engineering, surveying and planning firm. "We need engineers to do grading design in the software" and not with manual methods to maintain the digital data integrity, he says.
McClure's Schug says his company "doesn't really do anything differently" for stakeless grading projects, but they have tightened up data management procedures. "It's forced us to be more organized with our project data," he says, noting that multiple design alternatives for a given project are deleted or renamed to avoid sending incorrect data to the field.
Data management has proven a huge task on the Texas State Highway 130 project, a 90-mile toll road soon to be under construction near Austin, as shown in Figure 3. The first phase of the project is being designed and built by a joint venture called Lone Star Infrastructure, which consists of over 20 companies. With over 150 people working on design, the team found it needed special tools to track files. "Initially we put all the data on a file server, but it was difficult to find files and we had no audit trail" for updating and deleting files, says Frank Henderson, LSI's director of Information Technology. With most design being done with MicroStation and GEOPAK from Bentley Systems, Inc., Exton, PA, the team added Bentley's ProjectWise to provide a common platform for content management.
"ProjectWise gives a central viewpoint for everyone working in design," says Henderson. Users access drawings, import survey data, manage file updates and a plethora of other tasks using ProjectWise. Users can see live updates of drawings used as reference files as other users update them. Drawing attributes can be used to automatically create plan-sheet title blocks, as shown in Figure 4. After implementing ProjectWise five months into design, Henderson says the team reduced the number of active drawings from 11,000 to 3,600 by weeding out duplicate and obsolete files.
Figure 4. Bentley's ProjectWis has helped designers automatically create title blocks based on drawing attributes. (Courtesy of Lone Star Infrastructure)
The increasing use of the design-build approach in public works projects like SH 130 means more projects require structured data management systems, says Randy Tardy, Bentley's industry director for transportation. "Without a centralized vault of information, it's not just the left hand not knowing what the right hand is doing--you have an octopus," he says. On DB projects, one team handles both design and construction, often concurrently. Traditionally, one firm or agency designs a project and another builds it.
Figure 5. Using Autodesk Map, designers can separate different aspects of multi-use projects into discrete layers linked to a master plan. (Courtesy of Timmons Group)
XML Takes Hold
As another aid to the data exchange process, eXtensible Markup Language (XML), is finding real-world applications. A variation of the Hypertext Markup Language (HTML) used to publish Web information, XML helps ease the transfer of data between various software platforms and also provides a format suitable for long-term data archival. The industry-specific version called LandXML has been tailored for land development projects, defining data formats for such elements as coordinate points, alignment data, and parcel geometry. The official version of the standard, LandXML 1.0, was released last year.
Timmons Group has used LandXML to transfer survey data to designers and exchange design data between disciplines. After downloading field data from data collectors, the firm's survey personnel use LDT Land Desktop to create DWG files with drawing entities and XML files with point, parcel, and surface data. The information is sent to engineers using AutoCAD's eTransmit feature, which automatically identifies associated files such as xrefs and fonts, and provides a record of what was sent and when.
The XML approach enables engineers to "bring in the information they want, when they want it," says Timmons' Carris. Previously, Timmons surveyors would copy an entire LDT project structure to an engineering working folder, duplicating much of the data also being maintained by surveyors. Timmons, which uses both AutoCAD and MicroStation, has used LandXML on large multi-use developments such as Magnolia Green, as shown in Figure 5. The firm has also relied on the ability to attach source files in Autodesk Map and allow users to see drawing updates in real time. Timmons is researching the use of XML to transfer design data to the field for construction purposes, but has yet to deploy it on actual projects, says Carris.
The Federal Highway Administration is incorporating LandXML-based data exchange in its Interactive Highway Safety Design Model (IHSDM), a software analysis package for evaluating safety and operational effects of geometric design on two-lane rural highways. IHSDM uses geometric data from design software to predict accident rates, traffic flow and other behavior, as shown in Figure 6.
Before LandXML was available, FHWA's IHSDM team was planning to develop separate interfaces to import data from several commercial roadway design packages. Now, since those packages can create XML files, multiple interfaces are unnecessary, says Ray Krammes, an FHWA highway research engineer. "Ease of getting geometric data into our software was key," he says. "LandXML solved that for us." IHSDM was released for public evaluation earlier this year.
Figure 6. FHWA's Interactive Highway Safety Design Model uses LandXML capabilities to Import geometry and predict roadway performance. (Courtesy of Federal Highway Administration)
Yet another factor calling for efficient data reuse is the nation's focus on infrastructure security. "People are looking to extend the shelf life of design information" and maintain accurate records after projects are built, says Terry Bennett, senior Civil Industry marketing manager in Autodesk's GIS division. "A lot of the information people used to take as rudimentary, low-resolution data would have a limited shelf life. With Homeland Security, it's a whole new ball game," he says. As such, Autodesk has strived to "marry" its GIS, CAD, and engineering products and encourage LandXML export capabilities to maintain data integrity, rather than perpetuate old processes such as digitizing or scanning plans, says Bennett.
Whether during planning, design, construction, or maintenance, CAD in the civil engineering world is taking on a data-centric approach, rather than a drawing-centric approach. Forward-thinking professionals will want to make sure they're equipped to hop on the data train at any stage.