Application of GNSS in Road Traffic and Construction
Qian M
Abstract—Global Navigation Satellite System (GNSS) plays a more and more important role in our society, especially in traffic field. In road traffic network, there are many applications of GNSS. For example, taxi, car rental companies, and shipping companies use GPS technology to track their vehicles and dispatch them reasonably and efficiently. Therefore, these companies can decrease costs and response to their customer quickly. Meanwhile, many traffic construction projects rely more and more on Global Positioning System (GPS) because of its high level of precision. It is mainly used to establish various road engineering control network and measure the control points, etc. Road builder use GPS devices scaling a map and estimating parameters such as slope and turning angle of a road which is important in road construction. This paper will talk about the application of GNSS in traffic field from two aspects: traffic navigation and road construction.
Index Terms—Global Navigation Satellite System, Road Traffic, Road Construction
INTRODUCTION
Global Positioning System
The Global Positioning System (GPS) is a space-based satellite navigation system that provides basic location and time information in all weather conditions, anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites.[1] The system provides critical capabilities to military, civil and commercial users around the world. It is maintained by the United States government and is freely accessible to anyone with a GPS receiver.
Principle of operation
GNSS works based on the real-time measurement of pseudo rang and carrier phase. The measurement of pseudo range is an approach that estimate the time signals travel from satellites to receivers, and multiply by the transmit speed with regarding of different environment noises. And the carrier phase measurement method compute the phase difference caused by Doppler shifts between reference carrier phase and received carrier phase, and estimate pseudo range. Generally, GNSS use four or more satellites to estimate pseudo range and calculate receiver's position by the trilateration. With the improvement of computer model and advanced devices, the accuracy of position estimation can reach to amazing millimeter-level. The figures below show the basic principal of GNSS.
a) Model of GNSS system b) Trilateration
Figure 1. GNSS Principal of operation (Image from google image)
Introduction of GNSS application in road traffic and construction
It is estimated that delays from congestion on highways, streets, and transit systems throughout the world result in productivity losses in the hundreds of billions of dollars annually. Other negative effects of congestion include property damage, personal injuries, increased air pollution, and inefficient fuel consumption.
The availability and accuracy of the Global Positioning System (GPS) offers increased efficiencies and safety for vehicles using highways, streets, and mass transit systems. Many of the problems associated with the routing and dispatch of commercial vehicles is significantly reduced or eliminated with the help of GPS. This is also true for the management of mass transit systems, road maintenance crews, and emergency vehicles.
Global Navigation Satellite System (GNSS) enables automatic vehicles to locate themselves quickly and precisely, and in-vehicle navigation systems are widely used throughout the world today. By combining GPS position technology with systems that can display geographic information or with systems that can automatically transmit data to display screens or computers, a new dimension in surface transportation is realized. With the help of this convenient technology, many fields including road traffic benefit a lot, which improved efficiency and accuracy.
Traffic Navigation
The usage of GPS in traffic field is so common nowadays. People can use GPS do anything relating to finding their way such as traveling, searching specific buildings or stores, estimating distance or time, etc. It makes our drive more easy and restful. Besides, GNSS have many other applications in traffic navigation field that we will talk about later.
Navigation model
There are thousands of GPS devices in markets, but almost all of them works in the same steps. First of all, inputting destination. Users entry destination information into GPS navigation devices by typing or point directly. Then, embedded processor will calculate several different referenced routes according to specific traffic situation cooperating with Geographic Information System (GIS), and also provide the most optimal route for user. (A geographic information system (GIS) stores, analyzes, and displays geographically referenced information provided in large part by GPS [2]. Today GIS is used to monitor vehicle location, making possible effective strategies that can keep transit vehicles on schedule and inform passengers of precise arrival times. Mass transit systems use this capability to track rail, bus, and other services to improve on-time performance. (see Figure 2))
Figure 2. Geographic Information System (GIS)
After calculating routes, it comes to the core step of navigation: Navigating during moving. GPS devices continuously receive signals sent from different satellites so that they can figure out the user's information including position, velocity, and time. Finally, processor match this information with stored map, and instruct driver by a visible or audible way. In practice, many advanced methods are used to eliminate errors and improve practicability such as adding inertial sensor. [3]
Applications in road traffic
Based on the model we talked above, many road traffic applications of GNSS realized.
Road user charging (RUC) [4]
The payment methods for road usage have received a great attention during the past two decades. More recently, new advances in ICT (information and communication technologies) have encouraged researchers all around the world to develop automatic charging systems aiming at avoiding manual payments at toll plazas while enabling administrations to deploy charging schemes capable to reduce congestion and pollution. The recent application of Global Navigation
Satellite Systems (GNSS) on these charging platforms can present important advances.
Essentially, GNSS-based RUC use geographic positions to locate vehicles in charging areas or roads, and this information is sent to the operator's back office to finally create the bill. For example, the European Union is promoting the European Electronic Tolling Service (EETS) [5] as an interoperable system throughout Europe on the basis of these technologies.
Figure 3. GNSS-based RUC system
In GNSS-based RUC, information from the GNSS sensor is used to locate vehicles at charging places.
The use of GNSS as the main positioning technology to charge users for the road usage, has many benefits related to flexibility and deployment costs.
Road Survey and Serve
Many nations use GPS to help survey their road and highway networks, by identifying the location of features on, near, or adjacent to the road networks. These include service stations, maintenance and emergency services and supplies, entry and exit ramps, damage to the road system, etc. The information serves as an input to the GIS data gathering process. This database of knowledge helps transportation agencies to reduce maintenance and service costs and enhances the safety of drivers using the roads.
Tracking and Forecasting
Using GPS technology to help track and forecast the movement of freight has made a logistical revolution, including an application known as time-definite delivery. In time-definite delivery, trucking companies use GPS for tracking to guarantee delivery and pick-up at the time promised, whether over short distances or across time zones. When an order comes in, a dispatcher punches a computer function, and a list of trucks appears on the screen, displaying a full array of detailed information on the status of each of them. If a truck is running late or strays off route, an alert is sent to the dispatcher.
This is a great improvement of vehicle management for vehicle operation companies, which improved their efficiency and reduced losses.
Drive Warning for safety
With the continuous modernization of GPS, one can expect even more effective systems for crash prevention, distress alerts and position notification, electronic mapping, and in-vehicle navigation with audible instructions.
Research is underway to provide warnings to drivers of potential critical situations, such as traffic violations or crashes. Additional research is being conducted to examine the potential for minimal vehicle control when there is a clear need for action, such as the pre-deployment of air bags. The position information provided by GPS is an integral part of this research.
Intelligent Transportation Systems (ITS)
GPS is an essential element in the future of Intelligent Transportation Systems (ITS). ITS encompasses a broad range of communications-based information and electronics technologies. Research is being conducted in the area of advanced driver assistance systems, which include road departure and lane change collision avoidance systems. These systems need to estimate the position of a vehicle relative to lane and road edge with an accuracy of 10 centimeters.
Take google driverless car[6] as an example, currently (as of June 2014), the navigation system works with a very high definition inch-precision map of the area the vehicle is expected to use, including how high the traffic lights are; in addition to on-board systems, some computation is performed on remote computer farms.
Road Construction
GPS measurement technology has a wide range of application in road construction. It is highly precise and efficient compare with conventional measurement techniques. Global Navigation Satellite System has an obvious advantage to accomplish different kinds of road construction work. As few construction sites as possible, which are finished as quickly as possible – that's what everyone who uses the roads wants. Only if all operations at a construction site proceed without trouble can this be attained. Because if processes are reciprocally coordinated with precision, this enables the work to be completed more quickly and with optimum results.
The main usage of GPS application in road construction engineering are their location function. It determines the three-dimensional coordinates of a ground point by receiving satellite's information. The accuracy of GPS technology in road construction can be up to centimeter-level, which can fully satisfy the requirements of road detection, design, and construction. There are several common applications in this fields.
Application in Road Construction Field
Control Measurement
Conventional measurement methods are influenced by many factors such as weather and intervisibility condition. And it's time-consuming and poorly precise. However, with the help of GPS technology which build on control network, the accuracy is improved. Engineers can obtain high precise data all day with high speed, which fully satisfy the control measure requirement of super-large projects such as bridge and tunnel construction.
b) Making large scale topographic map
With the development of GPS technology and aerial remote sensing techniques in road construction field, GPS technology is used to make large scale topographic maps. We know that the route selection is based on a large scale map, which is an important pre-work of road construction. Traditionally, engineers have to build measure network at first, and then measure landform segment by segment. Again, this is time-consuming and not efficient, and it needs more laborers which is cost-ineffective. But now engineers can make a large scale map easily with the help of dynamic real-time GPS measurement. What they should do is just collect positioning information by GPS receiver to configure a set of scattered data, and the rest of the work can be done by computer graphics software efficiently. The benefit of using GPS technology to make maps is not only time-saving but also improves accuracy.
Stakeout measurement
Nowadays, GPS technology not only have good hardware equipment, but also plenty of software systems. During the process of route selection, it is pivotal to accurately build the road to meet the requirements according to the design specifications. The real-time dynamic GPS technology in stakeout measurement process is easy. Concretely, collecting data with proper intervals, and then selecting a known point as reference station to determine other positions. Finally put this data into a computer, and select route with the help of Auto CAD software. It's extremely convenient, and the accuracy is pretty high, which can be up to centimeter level. With the continuous advancement and improvement of dynamic GPS measurement technology, it will play a fundamental role in road construction fields.
Deformation observation
Dynamic real-time GPS deformation monitoring network can achieve millimeter-level accuracy in deformation observation of road construction. For examples, this technique is used in the cast situ beam deformation observation, embankment settlement observation, and tunnel construction deformation observation. Its accuracy is an order magnitude great than traditional approach, which has a broad prospects. For example, In order to study crustal deformation in the Taiwan-Luzon region [7], the data from annual surveys are processed together with data from 20 permanent stations in the Taiwan area and IGS stations in the Asia-Pacific region. Finally researcher found that the Chinese continental margin is moving in directions of 102°–112° with rates of 11–12 mm/yr relative to stable Eurasia, and a remarkable fault slips of 17–31 mm/yr across the Philippine fault system are detected with the help of GPS observation.
e) Road centerline survey
During the road construction process, center lines should be marked out on the actual ground after selecting route on a large scale topographic map. By using dynamic GPS measurement technology, engineers just simply enter the main point coordinates of the midline to GPS receiver, then system will automatically give the position to stake out points. Because of the position of each measurement points is independent, the accuracy of each points is consistent and rarely produce cumulative errors.
Cross-section and Vertical-section measurement
Engineers can draw the graphs of road cross-section and vertical-section by using the midline point coordinates and mapping software. Since all of the data needed for section graph are collected during making topographic maps with real-time kinematic technology, it greatly improved efficiency, and reduced the workload outside. In this measurement, GPS measurement technique have obvious advantages compared with traditional measurement methods in various aspects such as efficiency, accuracy, utility, and economy.
Advantages of using GPS technology in road construction
Firstly, GPS measurement has a very high accuracy. It works without the limitations of environment and distance. And it can works on the area with tough terrain.
Secondly, GPS measurement can greatly improve the quality of work and accuracy of results. It is not affected by human factors. The whole operation is processed entirely by microelectronic technology, computer control technology, and automatic recording, preprocessing, and calculating.
Third, GPSRTK technology revolutionize the mode of road measurement. Real-time Kinematic measure technology can obtain real-time three-dimensional coordinate of spatial location. This technique is very suitable for the survey of route, bridge, and tunnel. It can be directly on the ground to stakeout, and measure pile or point.
Fourth, GPS measurement can greatly reduce labor intensity. And it also reduced outside field workload. Generally, the operating efficiency of GPS measurement is 3 times more than that of conventional measurement methods.
Finally, both high-precision GPS altimetric measurement and leveling plane measurement are important area of GPS measurement applications. Especially in the current situation that road development need to meet the demands of different area condition. And GPS height measurement is undoubtedly an effective approach.
Conclusion
The widespread availability of GPS technology in recent years has fundamentally changed the traffic and transportation system in most of the developed countries. Transportation related GPS applications are numerous and range in complexity from simple uses such as collection of bus stop locations to sophisticated uses, such as real time vehicle tracking for Intelligent Transport System (ITS). In some developing countries, GPS in transportation sector is increasingly being used by the private companies. All of transportation field benefit from it.
Besides, the networking of the machinery is a very promising aspect for improving the quality in road construction, while at the same time saving time and money through quick completion of work at construction sites. With the help of GNSS, trucks, pavers and rollers deployed at the construction site, and the position signal can be improved right down to centimeter precision in order to fulfill construction requirements. By combining GNSS and inertial sensor technology, even short distances – under bridges, for example – can be circumvented.
In conclude, the development of GNSS technology leads a big leap in traffic field, and it improve the work efficiency and change the way people live.
References
[1] Wikipedia, http://en.wikipedia.org/wiki/Global_Positioning_System [accessed 10/20/2014]
[2] Official U.S. Government information about the Global Positioning System (GPS) and related topics, http://www.gps.gov/applications/roads/ [accessed 10/15/2014]
[3] Wikipedia, http://en.wikipedia.org/wiki/Inertial_measurement_unit [accessed 10/25/2014]
[4] Rafael Toledo-Moreo, and Jose Santa, "Performance Aspects of Navigation Systems for GNSS-Based Road User Charging"
[5] European Commission, "Decision 2009/750/EC of the European Commission on the definition of the European Electronic Toll Service and its technical elements," Document C(2009) 7547, October 2009.
[6] theguardian, http://www.theguardian.com/technology/2014/may/28/google-self-driving-car-how-does-it-work [accessed 10/26/2014]
[7] Shui-Beih Yu, Long-Chen Kuo, Raymundo S. Punongbayan and Emmanuel G. Ramos, Article first published online: 7 DEC 2012.
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