Request PDF on ResearchGate | Global Positioning System, Theory and Practice , 5th Edition | The Global Positioning System (GPS) is rapidly becoming as. The project of writing a Global Positioning System (GPS) book was con ceived DRM-free; Included format: PDF; ebooks can be used on all reading devices Dr . Lichtenegger is a geodesist with broad experience in both theory and practice. The Global Positioning System (GPS) is rap idly becoming as much a part of our daily lives as the Internet, and it is now being used to navigate and locate cars.
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Editorial Reviews. Review. " Although developed as a classroom text, the book is also useful as a reference source for professional surveyors and other GPS. Introduction to GPS: the Global Positioning System/Ahmed El-Rabbany. p. cm. Positioning System: Theory and Practice, 3rd ed., New York. Gps Theory and Practice Hofmann PDF - Free download as PDF File .pdf), Text File .txt) or read online for free. gps-theory-and-practice-hofmann-pdf.
We have a dedicated site for Ukraine. In , I was willing to commit myself to such a project. My first chief, Prof. Satellite orbits Hofmann- Wellenhof, Bernhard et al. The volume cogently presents the critical aspects and issues for users, along with the theory and details needed by students and developers alike. National Geodetic Survey in , where he was the Deputy Director.
In my opinion, the knowledge ofthe three authors should cover the wide spectrum of GPS. Read this book on SpringerLink cover old. Benjamin William Remondi for many reasons. It seems that you're in Ukraine. Software modules Hofmann-Wellenhof, Bernhard et al. Satellite signal Hofmann-Wellenhof, Bernhard et al. James Collins from Rockville, Maryland, U.
About this book This book is dedicated to Dr.
This book is dedicated to Dr. Reference systems Hofmann-Wellenhof, Bernhard et al. Peter Meissl, was an excellent theoretician; and my former chief, Prof. Lichtenegger's main interest is dedicated to GPS. Unfortunately, the timing was less than ideal for Dr. With more sophisticated techniques, one can globally synchronize clocks precisely. Presently achievable accuracy of time via GPS is some tens of nanoseconds, however one nanosecond is considered possible.
Ultra precise time transfer is possible few nanoseconds but requires advanced preparation, coordination of the two sites and tracking of speci c satellites during speci c time periods. Loran-C transmissions are also used for time dissemination and frequency reference purposes. Typically frequency accuracies of 1 part in and time accuracies of better than one microsecond can be achieved. Both USNO and NIST provide telephone voice messages accuracy 30 milliseconds , com- puter modem time transfer several milliseconds and remote synchronization of time bases 1 part in For real-time processing, special formats are employed.
There are two predominant formats currently being employed.
NMEA is a data format standard commonly employed for communications between ship-borne navigation electronics. GPS receivers output this format but do not accept it. Version 2.
With absolute time synchronization a special time synchronization receiver picks up the sig- nals from a single GPS satellite as it travels overhead. When clock y-overs are used, the satellite swings up over the two sites, one after the other. As it passes over each site, careful clock synchronization operations are performed to determine for each ground based clock relative to the satellite. Under typical conditions this 12 mode yields a clock synchronization error of around 50 nanoseconds.
The common view mode can be implemented when two distant sites have direct line-of-site access to the same GPS satellite at the same time. This mode yields synchronization errors of 10 nanoseconds or less. The multi-satellite common view mode involves four or more satellites that are being observed simultaneously from the two di erent clock sites.
Experts believe that they can achieve synchronization errors as small as 1 nanoseconds. With increasing sales volume, the costs are coming down and new applications are being reported in the news everyday.
However, very few applications of GPS in distributed systems and networking have been reported. Before discussing them, it is useful to take a brief look at other applications.
These can provide us new ideas about computer applications. Accurate frequency counters, time interval counters, frequency calibrators and phase comparators can be built using the GPS technology.
Accurate frequency and timing o set measurements can be made. In the GPS clock, one pulse per second signal exhibits an RMS pulse-to-pulse jitter of 1 nanosecond rather than 20 to 60 nanoseconds observed on 1 pps outputs from time based GPS receivers. It may provides services like the shortest route, etc. This is the most publicized application of GPS. These systems com- bine cellular data networks for communication, GPS for vehicle location, and geographic information system tools for mapping display.
With the aid of a wireless communication link, the emergency system communicates the GPS derived position information and the speci cs of the situation to the base station.
Several other emergency products exist currently. GPS technology can be used to plot aircraft altitude to a pitch of one-tenth of one degree. This is expected to reduce the number of people required in the control tower and cockpit. This allows them to determine the sizes and shapes of asteroids. To observe these events, astronomers have to use mobile telescopes placed in the predicted path of the shadow.
Timing signals from the GPS receiver are used to discipline a crystal oscillator that is used to time the event. During the Mariner and Voyager missions, spacecraft trajectories were planned so that radio signals from the spacecraft would transect a planets atmosphere.
Earth-based receivers were able to detect phase changes in the radio signals based on the refractivity of the atmosphere. Information obtained in this fashion could include atmospheric refractivity, density, pressure temperature and humidity. The GPS de- termined position is transmitted to the control station.
This information is used to track animals and for studying their nomadic patterns. Real time GPS along with digitized maps and possibly audio capability can provide useful navigational capabilities to the blind. Some of the uses are to track executives, to determine charges highway toll, charge depending on place of visit , to search for stolen items cars , to study the migratory patterns animals , to validate legal claims, etc. If the position of the airplane, and more importantly its vertical acceleration and tilt can be mon- itored with GPS, airborne gravimetric measurements can be corrected for non-gravitational accelerations.
Airborne gravimetric data can be used for scienti c research and natural resource exploration. A few of the e orts are described brie y here. It is 6 inches by 5. Motorola has also developed Traxar hand-held navigational computer. The transmissions include di erential GPS data.
The unit provides navigation based on the GPS data. They have introduced a computerized navigation system for automobiles. A car's location shows up on a detailed map. Drivers can pinpoint their location and track their driving progress in real time. Etak provides software for the maps as well as information on restaurants, hotels, entertainment and shopping in local areas.
By combining GPS tech- nology with pen computers, users can pinpoint their location in terms of latitude, longitude and altitude. It will facilitate paying of tolls using smart cards and GSM digital phone.
Here, GPS technology is used for location information. The software then conducts latency trials at various intervals between frame transmissions. Tests are claimed accurate to within microseconds.
The method is synchronous and, there- fore, requires that clocks at various nodes be kept closely synchronized. In networks there is a need to accommodate di erent time delays when multiple bit streams terminate in a single network element such as a long distance message switch.
For this purpose, synchronous communications systems relies on accurate frequencies being available. Stratum 1 ST-1 is the highest quality clock for a network. The GPS timing signal synchronizes a series of master clocks which in turn produce signals that are distributed throughout the network.
Most of these are our ideas that need to be explored further for feasibility and cost e ectiveness. The applications using precise timing provided by GPS are discussed rst. Position applications are discussed afterwards. This is similar to synchronized lights on roads. The motorists do not have to stop if various lights have synchronized clock.
Therefore, slotted access is more suitable for high-speed or long-distance networks. That is one reason why DQDB, which was being designed for metropolitan area network was slot based.
Same reasoning leads us to use slotted access for very high speed networks. In fact, slotted architectures have been proposed for all-optical, multi-gigabit networks. The main problem with slotted architectures is that a tight clock synchronization is required. This is now possible with GPS. The values assumed by any clock should be monotonically increasing. The rst property cannot be achieved absolutely, but only with some very high probability.
Good clock synchronization is essential for ordering of events e. Issues to be handled in clock synchronization include the fact that clocks do not always run at the precise rate, sites in a distributed system cannot communicate in nitely often, there 19 are always unpredictable delays in the message delivery, and faulty or malicious sites may provide incorrect or inconsistent time values to other sites.
Clock synchronization can be of two types: internal clock synchronization and external clock synchronization. Various time sources are described in Section 6. GPS clock can be used as a source for external clock synchronization. This technology has the potential to provide time accuracy of up to one nanosecond. Such accurate clock synchronization can help improve performance of distributed systems. In most architectures, there are some servers that cater to the time needs of their clients.
Only a few servers have a time provider external time source ; rest of the servers execute protocols to estimate the time. As GPS clocks become less expensive, more servers can act as primary sources. Use of less accurate GPS clocks to increase the fault tolerance is a possibility. Some of the implications could be less complicated protocols, improved fault tolerance, longer synchronization intervals, and better synchronization.
With GPS synchronized clocks, time stamps have higher reliability and may have higher resolution. With accurate clock times, a deadline timestamp on the packet can be used to nd the next packet to schedule. Using GPS technology, one can achieve a near global clock at intermediate switches in a network.
If all intermediate nodes have accurate clocks, an absolute time based real time communication protocol can be used to meet the deadline requirements. In this protocol each packet can be assigned an absolute time frame and all the intermediate points will schedule the communication to meet the deadline.
Similar approach can be taken for scheduling subtasks of real-time and mission-critical ap- plications. By maintaining a global clock, better guarantees can be given. Even in the design of ATM networks, the issue of one-way delay came up. With GPS synchronized clocks at the source and destination, the exact one-way delay between source and destination and to every switch can be easily measured with a single timestamp.
With GPS, exact one-way delay can be used for routing. Currently, the time-to-live eld is decremented by ms regardless of actual delay. With GPS synchronized clock, time-to-live could be the actual time.
The GPS derived position can also be used to locate replicated resources, e. A location dependent server migration approach to provide location independent computing is possible with the use of GPS derived parameters. All service scheduling decisions are made without regard to the location. There are many applications where knowing the location will help us adapt a di erent service strategy. Examples of such location-adaptive protocols are: 21 It has But from the car, it has an expensive and error-prone GPS provided location information can be used to make mobile computing decisions including which les to fetch and at what speed.
With GPS the same type of protection can be applied to electronic information. The information is usable only as long as the mobile computer is within the corporate boundary. In the former case, the connection has to be switched to a new base station and in the later case it can be handled by switching to a di erent channel. Hando s can be performed in a centralized fashion one central switch makes the decision or decentralized fashion mobile units make the decision.
In hando s, the signal strength from various base stations is measured and a decision re- garding a hando is made using the measurements obtained. Hando 's can be made based on the GPS derived position. Using the information about cell boundaries and the position, a decentralized hando can be initiated.
By this approach, passive listening to beacons can be avoided; complicated hando protocols can be simpli ed; intra-cell hand-overs can be detected easily; many unnecessary hando s can be avoided; and intelligent and optimistic hando techniques can be employed.
On the other hand, given location, velocity, and direction information, future location can be easily predicted. Signal strength based hando s may cause some interruption in service as the packets sent to the previous base have to be forwarded to the new base.
With GPS, the mobile units position, velocity, and direction information can be used to forecast the next base and prenegotiate the hand-over with all parties.
Adaptive power control algorithms try to optimize the power required for transmission. If the base is nearby, less power is used compared to when the base is far away. Such algorithms can use GPS derived position and direction information. These algorithms o er two fold advantage in cellular architectures by using less power and by allowing frequency reuse in the same cell. The rest is lost in space. With GPS provided position, the antennas can be directional.
This will help reduce the energy required, battery drainage, and, hence the weight of the units. Directional antennas are particularly helpful for long-distance wireless communication, e.
With directional antennas, the mobile units can talk to the least-busy base unit even if it is not closest unit.
This also helps in providing the minimum radiated RF pattern for covert communications. This increases the reuse of spectrum and helps in reducing the congestion. This process requires prior preparation and usually a permanent change. Using position based hando s, digitized cell layout information and directional antennas, cell splitting may be possible on a temporary basis.
The above approach can also be used in case of base station failures.
In military environment for example, operation desert storm , usually there are no pre-existing infrastructures. In such environments, it is better to use peer-to-peer 23 communication where signals from one soldier are transmitted and forwarded by another. Each mobile unit acts as an end-system as well as a router. Each unit is aware of the GPS position of other units and uses this information to nd the shortest route to the destination. To be e ective in these networks, optimum networking strategy must be adaptive with respect to the possible rates of platform movements.
Approaches that use RF link quality as the primary controlling parameters for the network routing decisions may not be adequate for highly mobile platforms. GPS provided position, heading, velocity, as well as, digital terrain topology information can be used in determining the optimum routing for packet data. The addresses have no relation to the physical location. For example, one may want to address a message to all police cars near Stanford university on route Such location addressing is feasible with GPS equipped receivers.
The GPS coordinates of the mobile unit will help in routing. Location depen- dent actions can also be performed. Intelligent robots can use position information usefully. Distributed robots a collection of robots for some task can be controlled better with GPS. Unmanned vehicles can navigate e ectively. Position based controls instructions can be executed by the robots location dependent actions. Maintenance crew carry GPS to locate the equipment.
Some of the problems are Selective Availability which degrades the achievable accuracies, low signal strength, weight and size of accurate GPS receivers, power consumption for mobile applications, temporary outage of the receiver as the receiver passes under obstructions, etc.