Grading a worksite is a critical element in preparing land for development. While it can be an expensive process, grading plays a critical role in laying out a mapped overview of jobsite development.
Today, machine technology has emerged to simplify the grading process and eliminate inefficiencies. Grade control is quickly being adopted on jobsites throughout the country, and the cost benefits of investing in grade control technology can enhance a contractor’s bottom line. Pairing a grade control system with a crawler dozer or motor grader is a great way to see a huge return on investment. A grade control system gives contractors the accuracy needed to bid more competitively and, in turn, win more jobs.
With grade control, the impact on an operation’s return on investment is almost immediate. For example, a developer plans to build a shopping center with a huge parking lot, a commons and a pond on a stretch of land. First, the developer will hire an engineer to build a 2-D representation of a 3-D land surface, or a topo. From this map, a design of the shopping center is then created.
Once the design is in place, contractors are brought in to prepare an estimate. Using a grade management system, contractors can topo the site themselves to verify the engineer’s quantities on the initial, 3-D contoured map of the existing site. This process is known as takeoff, which is comparing the plan quantity versus takeoff quantity using construction software. After completing his/her own accurate estimate, the contractor can create a competitive bid and win the contract.
Next, the contractor creates a 3-D model from the digital design, and then he/she will localize it and integrate the model into the on-site data collector and grade control machine. With the system ready to go, the contractor’s accuracy is improved, reducing the number of passes for successful job completion. Grade control drastically eliminates the need for grade stakes and additional workers on the jobsite, even during the verification process.
Grade Control Systems
There are many grade control systems available in the market today:
- Entry-level 2-D systems —The 2-D grade control system allows operators to set up a laser transmitter to cut to their desired grade, on both flat and sloping surfaces. The 2-D system uses angle sensors and rotational sensors to calculate the cross slope of either side of the blade, as well as a laser receiver to provide elevation control. Using a motor grader or crawler dozer, the system allows stringline, previous pass or curb and gutter tracing. With the laser receivers, operators can use the system for fine grading plane surfaces. The 2-D grade control system is ideal for applications with tight tolerances and finished grade work. Often, these systems come with a control box that includes software with a powerful range of features specifically designed for lift and/or tilt control on dozers and motor graders.
- 3-D systems —With a 3-D grade control system, the job’s design elevations are input into the crawler dozer’s or motor grader’s control box. A receiver on the machine reads the GPS signals received by an elevated antenna, as well as correctional data transmitted by a jobsite-based station to calculate an accurate, cutting-edge position. The control box’s computer compares the cutting-edge position to the design elevations and then displays cut-and-fill information. A 3-D system is best for complex contours. Automatic systems for both 2-D and 3-D even adjust the blade for the operator. Both methods allow you to achieve a precise height and angle, while using an exact amount of materials and manpower to complete the job.
- Robotic total stations —Robotic total stations are convenient when access to the sky is limited, such as on a project involving work inside a building or tunnel. They are 3-D positioning sensors for a 3-D grade control system. The sensor is an electro-mechanic and optical positioning device. It works anywhere a view of the sky is obstructed. Also, it is one of the most accurate positioning sensors available for 3-D grade control applications.
- Millimeter GPS system —An MMGPS combines the advantages of a laser with a GPS into one versatile, easy-to-use system. This technology can improve grading accuracy up to 300 percent over most 3-D machine systems. The MMGPS transmitter sends out a wall of light 33 feet tall and up to 1,000 feet in diameter, and with a machine control sensor added to the existing GPS system, the vertical accuracy is enhanced considerably.
Grade Control WorkFlow
Now, you have picked a grade control system that best suits the needs of your jobsite. Once you are ready to begin a project, it is critical to properly implement grade control to ensure your investment is worth the while. Since contractors are reducing their operating expenses with this technology, grade control impacts them significantly throughout the entire work cycle. To see efficient return on investment, it’s important for contractors to execute flawless grade control workflow, a step-by-step process to help them complete jobs and maximize ROI while using grade control technology. Walk through a day in the life of a contractor utilizing grade control:
- Setup/Topo—An engineer establishes four control points for a particular jobsite through specific measurements. The engineer will measure control points with a rover to establish the complete jobsite. Then, the engineer will create a topo of the jobsite. Wherever site development will occur, the engineer covers the entire jobsite to ensure all measurements are recorded. The topo will map out all of the elevation changes across the site, and the engineer will create the site design after all measurements are ensured and completed.
- Design—The jobsite design establishes the location of all the structures that will be built, including underground utilities, parking lots and everything else the landowner wants to build on the site.
- Takeoff/Estimate—In the takeoff/estimate portion of grade control workflow, contractors compiling bids will compare what the design engineer has provided for quantities on the site. Contractors will then verify utilities. Contractors will also confirm the material that will