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Use of Automated Machine Guidance within the Transportation Industry (2018)

Chapter: Chapter 2: Basic AMG Workflow Processes

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Suggested Citation:"Chapter 2: Basic AMG Workflow Processes." National Academies of Sciences, Engineering, and Medicine. 2018. Use of Automated Machine Guidance within the Transportation Industry. Washington, DC: The National Academies Press. doi: 10.17226/25084.
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Suggested Citation:"Chapter 2: Basic AMG Workflow Processes." National Academies of Sciences, Engineering, and Medicine. 2018. Use of Automated Machine Guidance within the Transportation Industry. Washington, DC: The National Academies Press. doi: 10.17226/25084.
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Suggested Citation:"Chapter 2: Basic AMG Workflow Processes." National Academies of Sciences, Engineering, and Medicine. 2018. Use of Automated Machine Guidance within the Transportation Industry. Washington, DC: The National Academies Press. doi: 10.17226/25084.
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Suggested Citation:"Chapter 2: Basic AMG Workflow Processes." National Academies of Sciences, Engineering, and Medicine. 2018. Use of Automated Machine Guidance within the Transportation Industry. Washington, DC: The National Academies Press. doi: 10.17226/25084.
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Suggested Citation:"Chapter 2: Basic AMG Workflow Processes." National Academies of Sciences, Engineering, and Medicine. 2018. Use of Automated Machine Guidance within the Transportation Industry. Washington, DC: The National Academies Press. doi: 10.17226/25084.
×
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Suggested Citation:"Chapter 2: Basic AMG Workflow Processes." National Academies of Sciences, Engineering, and Medicine. 2018. Use of Automated Machine Guidance within the Transportation Industry. Washington, DC: The National Academies Press. doi: 10.17226/25084.
×
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Suggested Citation:"Chapter 2: Basic AMG Workflow Processes." National Academies of Sciences, Engineering, and Medicine. 2018. Use of Automated Machine Guidance within the Transportation Industry. Washington, DC: The National Academies Press. doi: 10.17226/25084.
×
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Suggested Citation:"Chapter 2: Basic AMG Workflow Processes." National Academies of Sciences, Engineering, and Medicine. 2018. Use of Automated Machine Guidance within the Transportation Industry. Washington, DC: The National Academies Press. doi: 10.17226/25084.
×
Page 13
Page 14
Suggested Citation:"Chapter 2: Basic AMG Workflow Processes." National Academies of Sciences, Engineering, and Medicine. 2018. Use of Automated Machine Guidance within the Transportation Industry. Washington, DC: The National Academies Press. doi: 10.17226/25084.
×
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Suggested Citation:"Chapter 2: Basic AMG Workflow Processes." National Academies of Sciences, Engineering, and Medicine. 2018. Use of Automated Machine Guidance within the Transportation Industry. Washington, DC: The National Academies Press. doi: 10.17226/25084.
×
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Suggested Citation:"Chapter 2: Basic AMG Workflow Processes." National Academies of Sciences, Engineering, and Medicine. 2018. Use of Automated Machine Guidance within the Transportation Industry. Washington, DC: The National Academies Press. doi: 10.17226/25084.
×
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NCHRP Project 10-77 6 CHAPTER 2: BASIC AMG WORKFLOW PROCESSES Integrating AMG into transportation projects involves many decisions and workflow processes, including selection of surveying methods and technologies, software design and engineering analytic tools, machine systems, sensor technologies, data interoperability and transfer mechanisms, human- machine interaction during construction and training (Fig. 2-1). The set of simplified workflow diagrams and narratives that follow reflect the spectrum of processes and technologies that are organized according to these topics: 1. Surveying preparation workflow processes, 2. Roadway design workflow processes, 3. Contractor data preparation workflow processes, and 4. Overall integrated AMG workflow processes. The accompanying narrative attempts to concisely describe the processes involved with the workflow steps first to establish a baseline for the remainder of the report, and, second, to appreciate that AMG is best positioned to succeed when survey, design, and construction processes are coordinated. Understanding these AMG workflow processes is also important for developing effective guide specifications for implementing AMG where critical roles and responsibilities can be defined. In discussions with stakeholders in AMG processes, data interoperability was identified in virtually all the workflow processes as a key factor in providing an efficient AMG process. In the future, data interoperability will continue to be an area of desired AMG technology advancement. D at a P re pa ra tio n fo r 3 D PROJECT DESIGN CONCEPT/SURVEYING CONTRACTOR AMG DESIGN AMG IMPLEMENTATION D es ig n C on ce pt P ro je ct S ur ve y Se le ct R ef er en ce S ys te m Es ta bl is h C on tro l P oi nt s D ev el op W or k P la n Ex ec ut e W or k P la n Fu se D at a C he ck Q ua lit y G eo m et ric D es ig n E nv iro nm en ta l S tu dy R ig ht -o f-W ay A cq ui si tio n C on tra ct s & Le tti ng C on v. to H ar dw ar e A pp . F or m at M od el V er ifi ca tio n M in or A dd iti on al D at a P re p. S yn c. F ie ld /D es ig n C on tro ls C us to m iz e M od el fo r O pe ra to r In c. M od el in to A M G E qu ip . E xe cu te A M G W or k P la n Fi el d Q ua lit y V er ifi ca tio n P ub lic In pu t Figure 2-1. Elements of the AMG Workflow Processes SURVEYING WORKFLOW This section and the accompanying Fig. 2-2, describe and show the linkages between the AMG surveying workflow processes. Select Reference System The first step in designing a proposed roadway or other construction project is to complete the field survey. To begin this process a reference system must be chosen. Choosing a reference system is very important because all parties involved must reference the chosen system throughout the project. Examples of reference systems for a project are the National Spatial Reference System; state plane coordinate systems. local coordinate systems (e.g., county coordinate systems). With very rare exceptions, the coordinate system must accommodate the curvature of the earth in some way, because

NCHRP Project 10-77 7 noticeable errors will occur for project much less that one mile in length if the curvature effect is not recognized. Establishing a reference system that is unique to a project (e.g., setting an arbitrary local reference point to x = 0, y = 0, z = 0) is not recommended. Establish Project Control-Monumentation and Metadata After the owner has decided on a reference system, survey control monuments must be set. The monuments are positioned to bracket the job and used as check points throughout the project. Monuments should be outside the jobsite construction footprint but within the original reference network. The more frequently the points are within the required interval, the more accurate the survey will be. In most cases, the control monuments will be based on static GPS sessions based on National Geodetic Survey (NGS) requirements for the desired accuracy. Elevations will normally be based on 3-wire level techniques (i.e., uses average of three readings) using a precise automatic level or with digital levels that will produce required elevation accuracies. Develop Work Plan to Locate Terrain and Features In this step, the surveyor must decide on methods for obtaining the desired terrain data for the project, such as light detection and ranging (LIDAR); stationary terrestrial laser scanning; photogrammetry; and ground survey (e.g., using a total station). This decision on selection of the survey method affects the overall quality of the survey. This process normally involves the surveyor analyzing the project requirements and defining the accuracy and precision that will satisfy the end user(s). Best practice in this step is for the surveyor to discuss the error budget with the designer and other contributing parties so that the tolerance is understood by designers and contractors. Execute Work Plan Using the survey method chosen in the previous step, the survey crew will collect the field data needed for the project. Execution of the survey plan can be hindered depending on the method chosen. Seasonal and environmental constraints, such as heavy snow fall and sun angles, can restrict when and how the plan is executed. Fuse Data All surveying information needs to be combined in a logical way during the data fusion process. The data fusion process may combine data from ground surveys, LIDAR, and photogrammetry. It must be recognized that although different data streams have different precisions and accuracies, the fused data must maintain the specified levels of precision and accuracy. The specified levels of precision and accuracy cannot be maintained if any of the data being fused is at lower precision or accuracy than what is required. The fused data is used to generate DTMs, planimetric maps overtop orthometric photos, and point clouds. Fusing all the data results in a compiled control file that still may need revision depending on the users’ needs. In the beginning phase of fusing the data, quality assurance is performed as a preliminary check on the control file prior to compiling data. Data from various sources can be utilized as independent checks in overlap areas. For example, photogrammetry or ground survey can be used to find artifacts, blunders, or gross errors in LIDAR data. Check Quality A final quality check is performed after surveying data is compiled. The data is physically checked in the field to confirm the data is correct and make sure the data is within the defined error

NCHRP Project 10-77 8 budget. Once this process is finished, the complete control file is created and sent out to all parties involved with the project. Figure 2-2. Survey Preparation Workflow Processes DESIGN PROCESS Once the survey data is collected and formatted, the results are used by the designers to prepare the design files. This narrative describes the process for a design-bid-build project. The process used for design-build and other more integrated project delivery systems will likely be similar, but more integrated between design and construction. The contracts office uses the design documents to prepare the bid documents. The design to bid document process involves input from several engineers and teams (see workflow Fig. 2-3). Once contract documents are published, and the decision is made to use AMG during the construction phase of the project, the contractor must make use of the information (2D paper and/or 3D electronic design drawings) provided by the designer to develop construction machine-ready files (see

NCHRP Project 10-77 9 workflow Fig. 2-4). The overall AMG workflow processes (see workflow Fig. 2-5) shows that there are many steps in completing this process. Discussed in the following are details involved with theses interconnected workflow processes. The overall AMG workflow processes are summarized in Fig 2-5(a) (overall) and Fig. 2-5(b) (subset for contractor documentation). Design Office Conceptualization The design office will initiate projects by developing an initial concept for the transportation project. This concept will provide sufficient information for surveyors to perform their initial data collection and for design disciplines to perform preliminary design work. Surveying As discussed earlier, surveyors are usually the first data collectors for a transportation project. They are responsible for capturing the elevations of the existing topographic surface and finding the location of key features such as existing buildings and utilities. Skilled operators are required to select the most suitable surveying hardware for a specific job, because it is important to use good judgment in obtaining measurements expeditiously with reasonable accuracy to strike a proper balance between cost and accuracy. Using up too much of the error budget in the first step of data collection and manipulation leads to low accuracy/precision. It is important to define break lines such as ridge tops, and valleys such as ditch bottoms. Locating key features such as utility access points is also important. Currently, most surveying data is collected digitally and passed on electronically to the design team. DOTs might send out their own survey crews to collect data either using traditional surveying methods or advanced technologies (e.g. LIDAR). If the exact depths of utilities are required, “pot holing” or various electronic tracking methods can be used to obtain accurate locations. Designers Develop Drawings or Models In a Design-Bid-Build project delivery system, the designers are responsible for developing the contract documents. In most cases the contract documents are two-dimensional (2D) paper plans or possibly electronic prints in .PDF format. Sometimes, an electronic three-dimensional (3D) model may be available or included in the contract documents. The designer will use information obtained from surveyors such as existing ground surface surveys and the location of important existing features such as utilities to design the facility that will be constructed. Three dimensional (3D) electronic models are often developed by designers, even if the contract documents are provided only in 2D format. In such instances, the designer uses the design application software to generate plan, profile and cross-sectional views from the 3D model. Therefore, it is possible for a 3D model to be part of the design process, yet not part of the contract documents. Project Letting and Award In the traditional design-bid-build project delivery, the agency will submit the contract documents with the 2D plans and the winning contractor has the option to use AMG. However, in most cases, if a 3D electronic model is passed along to a contractor, it will not be part of the contract documents and the contractor will have to sign a waiver which declares that electronic model is for information only and not part of the contract documents. The contactors can use the model at their own risk to develop and customize 3D models for their own use.

NCHRP Project 10-77 10 Figure 2-3. Design Workflow Processes CONTRACTOR DATA PREPARATION Decisions about Using AMG When contractors are deciding whether a project is a candidate for employing AMG technology, certain factors should be considered. These factors are: time constraints (e.g., what deadlines are driving the project?); project size (e.g., Do bigger projects normally have higher priority for AMG?); equipment availability (e.g., is AMG-ready equipment already in use on other projects? Is buying, renting or leasing an option?); and availability of skilled labor (e.g., Are there enough trained operators to cover the project scope of work?). If contractors decide to use AMG, they could subcontract with an independent modeler or take responsibility for developing a 3D project model.

NCHRP Project 10-77 11 Data Preparation for 3D Conversion If the decision is made to use AMG, the contractor will need to develop a model specifically for construction use (Fig. 2-5(b)). If the designer developed a 3D model, it may be possible to enhance and convert that model so it is suitable for construction. Otherwise, it may be necessary to use 2D data or other information to develop the construction model. Some contractors choose to develop their own 3D models from scratch, even if the agency provide a 3D model. The rationale is that the contractor may have a very efficient system for developing the model and the contractor model and the agency model can be compared to avoid mistakes. The construction modeler may be able to obtain a 2D electronic file that will be helpful (e.g., in proprietary CADD format; vector .pdf; non-vector .pdf; or other) or, as a last resort, 2D paper drawings can be used. Nonetheless, the modeler must have a software application that can perform the data preparation tasks. This software could be the same software that the designer used to develop the original design although such software is more capable but could be harder to learn. The software could be provided by the hardware supplier, which is often the case because its capabilities are better matched with the needs of a construction modeler, or a third-party software could be selected. The result of the data preparation process are surface models and linework files. A final surface model that includes pavement surface will have to be developed; in addition, an existing surface model will have to be referenced. During the contractor’s data preparation process modeler will have to ensure that the template drops spacing is sufficiently close to provide for smooth surfaces in areas where there are horizontal and vertical curves, intersections, on- and off-ramps and other geometric transitions. This concept was explained elsewhere in the section on design. In some cases, a contractor may also develop a top of subgrade model for areas under the pavement surface while in many other cases, contractors may use machine based offsets to set the proper elevation of the subgrade, thus eliminating the need for a top of subgrade model. Conversion to Hardware Application Format as Necessary The construction model must be converted into machine control files in a hardware application format that can be used to guide the operator or control a piece of AMG equipment. When the construction model was developed using software provided by the AMG equipment vendor the machine control files can be output directly from that software. Some third-party software can provide machine control files for most AMG equipment. However, if the construction model has been developed using software that is primarily intended for developing 3D design models, it may be necessary to import the construction model to the AMG equipment vendor’s software to output the machine control files. Model Quality Control In the model quality control process, contractors visually examine the model to ensure that it can be constructed and that it appears to carry out the design intent. In some cases, the design model and the construction model can be compared directly to detect differences. Also, returning the construction model to the designer for similar examination may be an additional quality assurance step. If the construction model is returned to the designer, it must be returned in a format that can be accessed by the designer. Minor Additional Data Preparation by Field Personnel as Necessary Contractor field personnel may need to make additional minor edits to the contractor version of the model that was developed. For example, the models may multiple layers and only one layer may be applicable to a task that is to be performed by a machine operator. By turning on or off layers, field personnel can show only those that would be important for the task. Other minor preparation items may include changing colors of features, defining certain areas, or trimming lines.

NCHRP Project 10-77 12 Verify Existing Control Points After data preparation has been completed for the construction model, contractors will conduct a field survey using their own surveying equipment. The goal of the survey process is to locate and record the control points for the project according to the contractor’s surveying equipment. This process can go smoothly unless there are major discrepancies between the contractor’s field locations and original survey locations. If the project is a grading project or another type of project where GNSS is being used, before surveying begins, the contactor must take the key step of setting up a base station. The base station must be set up in a fixed location where it is clear of trees, tall buildings, or other objects that may obstruct connections between the base station and overhead satellites. Selecting a poor location for the base station may result in lower levels of accuracy, and when higher levels of accuracy are required, selecting the optimal base station location is crucial. After the base station has been properly set up, the survey can begin. Paving and subgrade preparation projects may require a higher level of accuracy than general grading projects, and, in most cases, GNSS locations will not have sufficient accuracy. For these projects, total stations or high accuracy GNSS techniques will have to be used to locate the control points because location accuracy is improved by occupying control points for longer times and averaging readings. Synchronize Field Control and Design Control After the field data is completely obtained through surveying by the contractor, the control point locations from the field survey and the design model are brought together and synchronized. This is done through hardware supplier provided application software. If there are major discrepancies between the two sets of data, they will be identified by the software and the contractor or designer will need to adjust accordingly. If no problems are identified through synchronization, the file is complete with three data components: linework data, surface data, and (just added in this step) calibration (synchronization) data. Synchronizing field control with design control not only is an important data component for automatic machine guidance, but also is very useful as a quality control/quality assurance tool because it gives the contractor final verification of the data quality before the final steps are taken to begin construction.

NCHRP Project 10-77 13 Figure 2-4. Contractor Data Preparation Workflow Processes Customize Model for Operator Use Depending on the actual need, the model can be further customized to best fit the operator’s specific machine. This can be done by turning on the layers that represent the surface that the machine is grading (such as subgrade or final surface) and turning off the other layers to give an uncluttered view of the design model. Also, the model can be “trimmed” to focus only on the area where the machine will work. Sensitive areas can also be marked as off limits for machine operation. Of course, the type of work should be properly matched with equipment ahead of time. A software application from the hardware supplier or the third party would be utilized during this process. A person who is trained to operate the software is also needed.

NCHRP Project 10-77 14 Implement Model into AMG-Ready Equipment Now, the machine control file is ready to be uploaded to the equipment. Basically, there are three types of files would be imported into the equipment, including surface model, line-work model, and calibration file. Again, a software application either from hardware supplier or the third party would be needed as a basic tool as well as a person who is skilled at using the application. OVERALL AMG PROCESSES Execute AMG Work Plan In this process (Fig. 2-5(a)) the designed work plan is finally being executed. Throughout this process there could be equipment recalibration and accommodation for design changes. Quality Control With AMG-ready equipment in operation, a final check should be performed as a part of quality control effort. If GNSS equipment is being used, often, a rover can be used to check the accuracy of the final surface daily. A total station or traditional surveying equipment could also be used to perform this check; this would be preferable, because it would provide more of an independent check in comparison to using a GNSS rover. For example, if there is an error in the GNSS base station, such an error would not be detected by a GNSS rover that was referencing the same base station. Additionally, the ground- engaging equipment should be placed on a benchmark to further check if the machine control elevation and location matches with the bench mark elevation and location. The contractor will periodically or even daily do checks on the machinery. Sometimes the result of these checks will require recalibration of the machinery as blades may wear and other machinery changes.

NCHRP Project 10-77 15 Figure 2-5(a). Overall AMG Workflow Processes

NCHRP Project 10-77 16 Figure 2-5(b). Contractor Documentation Subset of Overall AMG Workflow Processes

Next: Chapter 3: AMG Information and Lexicon »
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TRB's National Cooperative Highway Research Program (NCHRP) Web-Only Document 250: Use of Automated Machine Guidance within the Transportation Industry studies automated machine guidance (AMG) implementation barriers and develop strategies for effective implementation of AMG technology in construction operations. AMG links design software with construction equipment to direct the operations of construction machinery with a high level of precision, and improve the speed and accuracy of the construction process. AMG technology may improve the overall quality, safety, and efficiency of transportation project construction.

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