Automated machine control during the construction phase, especially in earthwork activities, is changing the way project members interact. Formerly, the surveyor took the design and laid it out in the field. If there were any problems with the way the design fit with existing or proposed contours or other planimetric details, this often was the first time they were discovered. The process of construction setting out used to involve laying out elements of the design at full scale (1:1). If there were problems, the surveyor captured the 3-D relationship of the design and the conflicting elements so that the designer then could adjust the design to make it work. The surveyor then would return to the field and try setting it out again. If successful, the contractor built the project, basing it all on the surveyor’s marks, and any supplemental surveying the contractor might do to fill in gaps.
As the project progressed, the surveyor, engineer, or contractor performed quality control and quality assurance activity. Once finished, the surveyor often was called upon to determine exactly what was constructed so that it could be documented properly in an "as-built."
Today, things have changed. The engineer creates plans, which may or may not be digital.
Even if the documents are electronic, they may not be truly 3-D from the perspective of the machine-control system. An intermediary must check the digital data to make sure it properly represents the world to be constructed. If the plans are exact electronic analogues to paper ones, then the 3-D world of the design must be "constructed" using those plans. Whether or not the plans are truly 3-D, the design to be constructed must be checked carefully (electronically) against other elements of the design in virtual space.
Similarly, the "fit" of the design to the existing lay of the land and other facilities that are on, above, or under the surface, must be checked in virtual space.
This intermediary may be the engineer, the surveyor, the contractor, or a third party who specializes in this function.
The electronic files then pass into the hands of the contractor, though they may be "touched" by others along the way. The files are loaded into the appropriate machines and the operators go to work. The business ends of these machines need to be controlled accurately based on where they are, which direction they are pointing, what the existing surface looks like—or what the existing surface might look like after it has been disturbed—and, of course, the design itself.
But for this stage to work, someone must calibrate the construction machines. Yes, with machine control, the grader, bulldozer, and scraper, in effect, become giant surveying tools. Differences in elevation, horizontal position, angles between cutting edges and the machines’ axes, and in some cases, the angle between the longitudinal axis of the machine and the axis of the cutting surface, must be determined accurately. These relationships should be checked regularly, because the machines can go "out of adjustment."
Testing jigs or testing processes must be used to verify that the machines continue to be calibrated properly. Machine operators certainly are given more responsibility in this area. They not only must drive the machines to one or more check stations and help determine if the calibration is correct, they also must do it at the appropriate frequency. Their responsibility also extends partially into the "does it fit?" world, as the process of shaping the earth at true scale often is the first time the engineer’s design is realized.
If done properly, the project doesn’t leave the "does it fit?" question only to the machine operators. Others—who may use the same tools that drive the control of the machine’s blade, but in more of a standard surveying configuration—may check that the work is carried out correctly. Even the software on the machines and in the hands of the quality checkers bear a remarkable resemblance to each other.
Relationships between members of the project team and the expectations about their responsibilities must change, just as the process itself does. These advances result in further process changes to ensure that the information needs of the parties and the interests of the project owner are addressed sufficiently. Where the responsibility for performing a vital project inspection has changed from one project team member (or discipline) to another, the project manager must consider whether the new function is within the expertise and ability of the new person or entity. Reporting structures, the information that is reported, the manner in which it is reported, and to whom it is reported all can change.
Machine control has brought significant advances to the construction site. All the players in a project, including the construction manager, must look at the process to analyze and redraw the connections, the details of information flow, the analysis mechanisms, the points of decision, and the feedback response paths, to ensure projects get built properly, quickly, and efficiently.
Joseph V.R. Paiva, Ph.D., P.S., P.E., is a geomatics consultant. He can be reached at email@example.com.