Make up a plan and retell the text according to it.
Topic 3: The principles of GPS functioning
1. Read and translate the text:
A GPS receiver calculates an automobile’s position by precisely timing the signals sent by the GPS satellites high above the Earth. Each satellite continually transmits messages which include:
- the time the message was sent
- precise orbital information (the ephemeris)
- the general system health and rough orbits of all GPS satellites (the almanac).
The receiver measures the transit time of each message and computes the distance to each satellite. Geometric trilateration is used to combine these distances with the satellites' locations to obtain the position of the receiver. This position is then displayed, perhaps with a moving map display or latitude and longitude; elevation information may be included. Many GPS units also show derived information such as direction and speed, calculated from position changes.
Three satellites might seem enough to solve for position, since space has three dimensions. However, even a very small clock error multiplied by the very large speed of light—the speed at which satellite signals propagate—results in a large positional error. Therefore receivers use four or more satellites to solve for the receiver's location and time. The very accurately computed time is effectively hidden by most GPS applications, which use only the location. A few specialized GPS applications do however use the time; these include time transfer, traffic signal timing, and synchronization of cell phone base stations.
Although four satellites are required for normal operation, fewer apply in special cases. If one variable is already known, a receiver can determine its position using only three satellites. (For example, a ship or plane may have known elevation.) Some GPS receivers may use additional clues or assumptions (such as reusing the last known altitude, dead reckoning, inertial navigation, or including information from the vehicle computer) to give a degraded position when fewer than four satellites are visible.
2. Make up a plan and retell the text according to it.
Topic 4: Floating car data
1. Read and translate the text:
Floating car data (FCD) (also known as Floating Cellular Data) is a method to determine the traffic speed on the road network. It is based on the collection of localization data, speed, direction of travel and time information from driving vehicles. These data are the essential source for traffic information and for most intelligent transportation systems (ITS). This means that every appropriately equipped vehicle acts as a sensor for the road network. Based on these data, traffic jams can be identified, travel times can be calculated, and traffic reports can be instantly generated.
|
|
|
In contrast to traffic cameras, number plate recognition systems, and sensor loops embedded in the roadway, no additional hardware on the road network is necessary. Different types are possible:
Floating Cellular Data = cellular network data-based (CDMA, GSM, UMTS, GPRS): No special devices/hardware are necessary: every switched-on mobile phone becomes a traffic probe and is as such an anonymous source of information. The location of the mobile phone is determined using triangulation or the hand-over data stored by the network operator. As the GSM localization is less accurate than GPS based systems, lots of devices have to be tracked and complex algorithms need to be used to extract high-quality data (Care must be taken, for instance, not to misinterpret cellular phones on a high speed railway track parallel to the road as incredibly fast journeys along the road). However, the more congestion, the more cars, the more phones and thus more probes. In metropolitan areas where traffic data are most needed the distance between antennas is lower and thus the accuracy increases. FCD based on mobile phones believe to have significant advantages over GPS-based or conventional methods such as cameras or street embedded sensors: no infrastructure or hardware is needed to be built in cars or along the road. It is much less expensive, offers more coverage of more streets, it is faster to set up (no work zones) and needs less maintenance.
Wireless signal extraction is a new term in the ITS industry. Wireless signal extraction (WiSE) is a technology that pulls or extracts data from a wireless carrier’s network, after the data have been anonymized. The data are then used to provide traffic information. The resultant information can be used to provide drivers with real-time traffic conditions, to build historical databases of traffic information for planning purposes, and to give emergency response agencies both historical snapshots and real-time conditions to aid in their evacuation and emergency response management. WiSE technology provides traffic information on highways and arterials, which is an advantage over other technologies. Another advantage of WiSE technology is that it does not rely on equipment that has to be installed and maintained, such as sensors. This term was initially used by AirSage to describe its technology.
|
|
|
Electronic toll collection device data: ETC transponders, which are uniquely identifiable, may be read not only at toll collection points (e.g. toll bridges) but also at many non-toll locations.
GPS-based: A small number of cars (typically cars driving in a fleet, such as courier services and taxi drivers) are equipped with a box that contains a GPS receiver. The data are then communicated with the service provider using the regular on-board radio unit or via cellular network data (more expensive).
It is possible that FCD could be used as a surveillance method, although the companies deploying FCD systems give assurances that all data are anonymized in their systems, or kept sufficiently secure to prevent abuses.
Extended FCD (XFCD)
Additionally, efforts are underway to enable the use of Extended Floating Car Data (XFCD). Today’s cars are equipped with a range of sensors, some of which can be used to provide extended data. If the majority of the vehicles in a given area have activated their windscreen wipers, for example, then it is reasonable to assume it is raining (or snowing) in that area. Vehicle navigation systems could provide location and speed information (indicating traffic jams, etc.), while in-vehicle emergency response systems offer an important link for incident detection and management.
Some of the key issues that need to be addressed to make the use of XFCD possible are the communications options, sensor interfaces and interoperability. ERTICO is working with its partners and other key players to determine how best to go about implementing XFCD on a large scale. The communications question is significant, as the availability of packet-oriented mobile communications will have a huge impact on both the possible technical solutions of retrieving data from probe vehicles and the operational costs for running the service.
|
|
|
In addition, an on-board standard sensor interface will allow an economic use, independent of the specific floating car data implementation. Plus, the design of on-board logic, a transmission protocol, remote configuration of vehicle communication behavior and control centre operational procedures that are interoperable Europe-wide will greatly advance the use of XFCD.
2. Find Russian equivalents for:
- Floating Cellular Data
- hand-over data
- Wireless signal extraction
- In-vehicle emergency response systems
- Retrieving data
3. Say whether the given sentences true or false. Correct if necessary:
- A small number of cars (typically cars driving in a fleet, such as courier services and taxi drivers) are equipped with a box that contains a GPS receiver.
- Wireless signal extraction is not a new term in the ITS industry.
- Vehicle navigation systems could provide location and speed information (indicating traffic jams, etc.), while in-vehicle emergency response systems offer an important link for incident detection and management.
- The location of the mobile phone is determined using triangulation or the hand-over data stored by the driver himself.
- The resultant information can be used to provide drivers with real-time traffic conditions, to build historical databases of traffic information for planning purposes, and to give emergency response agencies both historical snapshots and real-time conditions to aid in their evacuation and emergency response management.
Дата добавления: 2018-05-12; просмотров: 338; Мы поможем в написании вашей работы! |
Мы поможем в написании ваших работ!