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2D VS 3D Grade Control for Excavators

Jun 17/2022

As construction sites become larger, more complex, and most importantly, more precisely planned, more and more machine control products are demanded by the construction industry. Since excavator is the most commonly used machine in construction, people have developed a variety of auxiliary and guided construction products to make the most of it. Among those products, the grade control system is the most widely-used excavator control system today. 

So, what is the difference between 2D and 3D grade control for excavators? We offer you a detailed comparative introduction regarding their principles, applications, advantages, etc.

Excavator grade control for digital construction

2D VS 3D Grade Control Principle

First of all, a concept needs to be clarified. When we talk about 2D or 3D grade control system for excavators, we do not refer to the models displayed on the control terminal. The terminal display model of 2D grade control can be a 3D model, and 3D grade control can be a 2D model.  

The 2D and 3D here represent two positioning algorithms. The 3D system is a guidance system based on positions and height, while the 2D system works only by height and tilt. 

① The principle of 2D excavator grade control system

The 2D grade control system allows operators to work on a single plane, whether it is flat or not, and whether it is a single or dual slope. Generally, the 2D excavator system is generally divided into two types: one based on the laser principle and the other on the ultrasonic principle. 

· Laser 2D grade control

The first type of 2D grade control uses a laser system. The laser receiver is used to provide height information and the sensor is used to provide slope information. By assigning the laser transmitter to cut to the desired slope on flat and curved surfaces, and using the laser receiver, the operator can grade the surface of the plane accurately. 

Laser 2D excavator grade control system principle

The laser receiver is installed on the excavator arm, but it is difficult to consistently capture the laser plane due to the high variation in elevation during the operation. Thus, it is important to use the reference value that the receiver passes through the plane each time.

· Ultrasonic 2D grade control

The second type of 2D grade control uses an ultrasonic system. The ultrasonic signal is transmitted vertically and then reflected onto a tensioned guide line or road edge. It retrieves the vertical distance by calculating the time it takes for the ultrasonic signal to return to the sensor. The ultrasonic 2D control system works in the millimeter range and always maintains a local relationship with the existing structure. Staking out the sample guide wire is a complex process that must be completed in advance. 

② The principle of 3D excavator grade control system

The 3D grade control system allows operators to add variable distances, such as a curved line or a curved trench. The 3D system is suitable for designing complex excavation projects such as large drainage projects. The 3D excavator system is generally divided into two types: one based on the tachymeter and the other on the GNSS. 

· GNSS 3D grade control

The GNSS 3D grade control system is a RTK & GNSS technology-based guidance system. It utilizes GNSS to get the accurate information on excavator positions, and uses IMU sensor modules (installed on excavator platforms, booms, sticks and buckets) to pinpoint excavator buckets. This waives the need to mark sites with physical signs because operators can view the plans besides the excavator on the display control terminal of the control system. 

GPS 3D excavator grade control system principle

At the same time, through the base station RTK signal or network RTK signal, the GNSS signal is corrected, so that the final positioning accuracy reaches 1-5 cm. 

· Tachymeter 3D grade control

For the tachymeter 3D grade control system, an automatic tachymeter is required, and a prism should be installed on excavators to track the target, with the automatic tachymeter and excavators communicating by radio. On excavators, the position of the bucket cutting edge is calculated by using slope and angle sensors, which is the same as that with the 2D laser control system or the 3D GNSS control system.  

The position of the tachymeter must be detected by a free stationing or installed at a known point with a directional port. The precise position of the excavator can then be calculated by polar point determination. The tachymeter 3D excavator system provides millimeter accuracy.  

The automatic tachymeter can only navigate one construction machine at a time and must maintain an uninterrupted line of sight from the prism at all times. Therefore, the tachymeter control system is best suitable for large open construction sites where one type of construction machinery is used. Although it requires surveying skills, expensive equipment, and the necessary line of sight, the tachymeter control system can serve as an alternative to the GNSS control system, especially in places without GNSS reception such as forests, narrow valleys, and underground.

2D VS 3D Grade Control Application

① 2D excavator grade control system - One man system

The 2D grade control system guides operators in the cab to control the height and lateral slope, allowing them to reach a specified digging depth, or to maintain a specific digging level. The 2D system is suitable for applications with tight tolerances. It is capable of completing easy work such as plane flatting, slope grading, slope deepening, and elevation.

Excavator 2d grade control system - One man system

② 3D excavator grade control system - For complex construction

In addition to positioning, the 3D grade control system compares the bucket tip position to a standard line and then displays cut and fill information. The 3D system is suitable for complex construction contours such as trenching slope work, embankments, and bridge headers. Meanwhile, it is also suitable for large earth moving projects such as dams, reclamation, landfills, and waste deposits. 

3D excavator grade control system - For complex construction

2D VS 3D Grade Control Benefits

① 2D excavator grade control system benefits

The 2D system is known for its lower cost. Its benefits include: 

- Improving safety
- Saving cost
- Maximizing machine utility
- Minimalizing training time
- Accurate slope and digging work
- Easy to adopt
- Slope control
- Real-time depth and distance

The 2017 "Technical Review of Automated System Application to Earthworks in Australia" shows that the 2D laser-leveling technology is the most widely-adopted technology (58%) in the Australian construction industry. 

Technology GPS Laser Remote Monitor Hybrid Excavator Tilt Rotator Total
# of companies 23 43 3 4 1 74
Percentage 31% 58% 4% 6% 1% 100%


② 3D excavator grade control system benefits

When dealing with large or long-term projects, the 3D grade control system provides more benefits, which include:
- Real-time information on depth, distance, and grading
- Accuracy and precise positioning
- Optimizing sites
- Reducing excavator downtime
- Reducing fuel cost Improving safety

Choose 2D or 3D Excavator Grade Control System?

Item 2D SYSTEM 3D SYSTEM
Application Ideal for flat planes and slopes Ideal for intricate planes, slopes, contours & complex curves
Reference Benchmarks Use an external point of reference (stringline, curb or laser) Use an internal point of reference (digital design plan)
Technology Use one or more of these sensing technologies: slope, rottion, sonic, laser Use one or more 2D senors + GPS/GNSS receiver or universl total station
Hardware Requires additional hardware such as laser level or sonic tracker Requires additional hardware such as base station, total station etc or Network RTK solution for operation
Cost Lower Higher
Adaptability Low adaptability to changing worksite conditions and plans Highly adaptability to changing worksite conditions or plans


The most common factors to consider when choosing 2D or 3D control system:

Price: The 2D is less costly than the 3D, but it has limited functional capabilities and lower accuracy. When it is determined that the 2D system can meet the complexity and accuracy of the job at hand, it may be chosen.

Functionality: The 2D is suitable for simple excavation depth and distance operations, while the 3D system offers more functionality to improve accuracy and project results when tracking machine positioning and slope specifications. Choose the 3D system if you seek advanced technology integrated with site plans.

Time: The 3D control system cuts off excessive downtime by waiving the need to manually set stakes and recalibrate the machine. However, compared to the 2D, the 3D system is more complex, and staff may require more training time. Choices should be made based on the combination of staff skills and project circumstances.

FJD 3D Excavator Grade Control System

FJD 3D excavator grade control system (FJD Excavator Guidance System) is a GNSS-based excavator guidance system for high accuracy (3cm).

FJD 3D GPS Excavator Grade Control System for Sale

It has been applied to sloping brushing, land leveling, wading operation and deep excavation.

References

1. "Grading: BIM. landscapingSMART. 3D-Machine Control Systems. Stormwater Management"
2. "Technical Review of Automated System Application to Earthworks in Australia". Pages 594-601 (2017 Proceedings of the 34rd ISARC, Taipei, Taiwan, ISBN 978-80-263-1371-7, ISSN 2413-5844).

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