15-02-2010, 08:21 PM
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ABSTRACT
In the beginning of the 19th century we had the industrial revolution, in the middle of the 20 th century we have the digital revolution, and in the dawn of the 21st century we have the communication revolution. The major innovation which upturned the communication revolution is the artificial satellite. Generally satellites use the latest technology for communication, remote sensing, weather forecasting and the like.
Global positioning system, usually called GPS are used to communicate with satellites and with receivers in the different parts of the world. This seminar aims to throw light into the technical details, advantages, pitfalls and major application areas of the GPS systems.
1. Introduction
Many of our decisions depend on the details of our immediate surroundings, and require information about specific places on the earth surface. In this regard, recent studies in information technologies have opened a vast potential in communication, analysis of spatial and temporary data. Data representing the real world can be stored and processed so that they can be represented later in a simplified form to suite specific needs. Such information is called geographical because it helps us to distinguish one place from another and to make decisions for one place that are appropriate for that location. Geographical information allows us to apply general principles to specific condition of each location, allows us to track what is happening at any place, and helps us to understand how one place differs from another. Spatial information is essential for effective planning and decision making at regional, national and global levels
Geographical information in the form of maps , photos taken from aircrafts and images collected from space borne platforms can be represented I digital form, this opens an enormous range of possibilities for communications ,analysis modeling, on accurate decision making but a degree of approximation .
GIS can be defined as computerized information storage processing and retrieval system that has hardware software specially designed to cope with geographically referenced spatial data
Information includes:
Techniques to input, sort geographical information, convert into digital form and store it in digital storage media
Methods for automated analysis for geographical data, to search for patterns, combine different kinds of data, make measurements find optimum sites or routes, and a host of other tasks
Methods to predict the outcomes of various scenarios, such as the effect of climate change on vegetation
Techniques for display of data in the form of maps, images and other kinds of display
Capabilities for output of result in the form of numbers and tables
Elements of GIS
Cartographic display system, spatial and attribute database, map digitizing system, DBMS, geographic analysis system, statistical analysis system and decision support system
Components of GIS
¢ Spatial and attribute database:
Central to the system is database- collection of maps and associated information in digital form. Since the database is concerned with earth surface features, it seem to comprise of two elements- the spatial database describing the geology of earth surface features, and an attribute database describing characteristics or quantities of these features
¢ Cartographic display system:
Surrounding the central database, we have a series of software components. The most basic of this is the Cartographic display system. The Cartographic display system allows one to take selected elements of the database and produce map output on the screen or some hard copy device such as printer or plotter
¢ Map digitizing system:
With the map digitizing system one can take existing paper maps and convert them into digital form, thus further developing the data base. In the most common method of digitizing one attaches the paper map to a digitizing tablet for board and then places the features of interest with a stylus according to the procedures required for digitizing. Scanners can also be used digitize data such as aerial photographs. The result is graphic image; rather then outlines of features that are created with a variety of standard graphics file formats for export these files are imported into GIS. CAD(computer assisted design) and COGO (Co-ordinate Geometry) are two examples of software systems the provide the ability to add digitized map information systems to the database, in addition to providing cartographic display capabilities .
¢ DBMS:
The next logical component in GIS is database management system, which is used to input manage and analyze attribute information along with the spatial data. DBMS aids to enter attribute data such as tabular information and statistics and subsequently extract specialized tabulations and statistical summaries to provide new tabular reports DBMS provide ability to analyze attribute data. Software that provides cartographic display, map digitizing and database query capabilities are often referred to as automated mapping and facilities management AM/FM system
¢ Geographic analysis system:
Up to this point, we have described a very powerful set of capabilities that the GIS offer, the ability to digitize spatial data and to attach attribute to the features stored; to analyze these data based on those attribute; and to map to the result.
A traditional DBMS cannot solve this problem because bedrock type and land use divisions simply do not share the same geography. Traditional database query is fine as long as we are taking about attributes belonging to the same features. For this we need a GIS. In fact, it is this ability to compare different features based on their common geographic occurrence that is hallmark of GIS. This analysis is accomplished by the process of overlay, thus named because it is identical in character to overlaying transparent maps of the two entity groups on top of one another. Thus the analytic capabilities of geographic analysis system and the DBMS play a vital role in extending the database through the addition of knowledge of relationships between features
¢ Image processing systems:
In addition to these essential GIS elements remotely sensed image and specialized statistical analysis are also important
¢ Statistical analysis system:
GIS incorporates a series of specialized routines for analyzing the statistical description of spatial data for inferences drawn from statistical procedures
¢ Decision support systems (DSS):
It constitutes a vital function of GIS. It helps in the construction of multi-criteria suitability maps, and address allocation decisions when there is multiple objectives involved while accounting for errors in the process. DSS provides a powerful tool in decision “ making for resource allocation
The Global Positioning System, usually called GPS (the US military refers to it as NAVSTAR), is an intermediate circular orbit (ICO) satellite navigation system used for determining one's precise location and providing a highly accurate time reference almost anywhere on Earth or in Earth orbit.
The first of 24 satellites that form the current GPS constellation (Block II) was placed into orbit on February 14, 1989. The 50th GPS satellite since the beginning in 1978 was launched March 21, 2004 aboard a Delta II rocket
2. GPS HISTORY
The initial concept of GPS began to take form soon after the launch of Sputnik in 1957. .... Some scientists and engineers realized that radio transmissions from a satellite in a well-defined orbit could indicate the position of a receiver on the ground" This knowledge resulted in the U.S. Navy's development and use of the "transit" system in the 1960's. This system, however, proved to be cumbersome to use and limited in terms of positioning accuracy.
Starting in the mid-1970s the U.S. Department of Defense (DOD) began the construction of today's GPS and has funded, operated, and maintained control of the system it developed. Eventually $12 billion dollars would take GPS from concept to completion. Full Operational Capacity (FOC) of GPS was reached on July 17, 1995 (U.S.C.G., 1996, www). At one point GPS was renamed NAVSTAR. This name, however, seems to be regularly ignored by system users and others. Although the primary use of GPS was thought to be for classified military operations, provisions were made for civilian use of the system. National security reasons, however, would require that civilian access to accurate positioning be intentionally degraded.
3. GPS ELEMENTS
GPS was designed as a system of radio navigation that utilizes "ranging" -- the measurement of distances to several satellites -- for determining location on ground, sea, or in the air. The system basically works by using radio frequencies for the broadcast of satellite positions and time. With an antenna and receiver a user can access these radio signals and process the information contained within to determine the "range", or distance, to the satellites. Such distances represent the radius of an imaginary sphere surrounding each satellite. With four or more known satellite positions the users' processor can determine a single intersection of these spheres and thus the positions of the receiver. The system is generally comprised of three segments:
The space segment
The control segment
The user segment
3.1 SPACE SEGMENT
The space segment consists of 24 satellites, each in its own orbit 11,000 nautical miles above the Earth. The user segment consists of receivers, which you can hold in usersâ„¢ hands or mount in usersâ„¢ vehicle. The control segment consists of ground stations located around the world that make sure the satellites are working properly
3.1.1 Orbit
The GPS space segment uses a total of 24 satellites in a constellation of six orbiting planes. This configuration provides for at least four equally- spaced satellites within each of the six orbital planes. The orbital path is continuous in relation to the earth, meaning that a satellite's orbit will follow the same path on the earth with each orbit. At 10,900nm (20,200km) GPS satellites are able to complete one orbit around the earth every 12 hours. GPS satellites orbit at a 55-degree inclination to the equatorial plane. This space segment configuration provides for a minimum of 5 satellites to be in view from any place on earth, fulfilling the necessary four needed for three-dimensional positioning.
31.2 Frequencies
The GPS satellite, like other telecommunication satellites, uses radio signal transmission for distribution of data used in positioning computations. Each satellite continuously transmits a composite spread spectrum signal on two L band frequencies. L1 transmits at 1575.42 MHz and L2 transmits at 1227.60MHz. Both carrier frequencies are phase-modulated with the Precise code (P-code). The L1 carrier is additionally phase-modulated with the Coarse/Acquisition-code. A Navigation Message is also modulated on the L1- C/A-code signal. Each satellite transmits a unique code, allowing the receiver to identify the different code of each satellite.
31.3 Codes
First observation of these codes would suggest that they are random. In fact, all GPS codes are Pseudo Random Noise (PRN) codes by design. With the appropriate receiver one can see that these codes actually follow a well - defined, predictable sequence. Receiving equipment is used to find the highest correlation between a known GPS code and the radio transmission of that code received by the user. Once a correlation is found the user is able to find the lag time between the known time of code broadcast and the time the code was received by the user. The lag is the time it takes the code to get from the GPS satellite to the user's receiver. This time can then be used to determine the distance between the known satellite position and the user position.
The broadcast of Coarse Acquisition Code (C/A-code) was designed for civilian applications of the GPS. The C/A-code is available to virtually anybody at any time, provided they have the right equipment.
Given the potential for harmful applications of the GPS, the designers of the system built into the C/A-codes what is known as selective availability. Selective availability is an intentional inaccuracy in a satellite's onboard clock that changes over time. This intentional inaccuracy is known as clock dither and is classified GPS information. The result of clock dither is essentially a degradation of navigational accuracy.
The broadcast of Precise-code (P-codes) was designed for military applications and is generally restricted to authorized personnel and organizations. The P-code is a 10 MHz PRN code carried on both L1 and L2. For additional security the Anti-Spoofing (A-S) mode can be engaged.
The Navigation Message is carried on the L1 frequency as 50Hz signal. This signal carries information concerning the satellite orbit position, clock corrections and other system parameters. GPS authorities may also degrade and falsify this information in an effort to limit civilian access to extremely accurate navigational techniques.
31.4 Time and pseudo-ranges
On board each GPS satellite is a highly accurate atomic clock. "These clocks are by nature very stable (they might gain or lose a second in 30,000 years)." In order for accurate measurements of time to happen between the GPS and the user, nearly exact synchronization is needed between satellite time and user time. Since the user's receiver is generally an inaccurate timepiece exact synchronization is not easily available.
Accurate positioning can be achieved, however, by using pseudo- ranges. A pseudo-range is an inaccurate distance established between a satellite and a receiver. Despite this inaccuracy, determining a distance between the receiver and a known satellite location provides a sphere of reference. The radius of this sphere of reference is equal to the pseudo-range established between the GPS satellite and the receiving unit. With four spheres of reference from four different satellites a user has the spatial positions needed for three dimensional positioning. The intersection point of these four spheres will result in an inaccurate location for the receiver. To gain a more accurate reading the user can adjust for the initial time inaccuracy by lowering or raising the amount of time lag originally determined. With time adjustments, additional computations can result in more accurate distances and thus greater accuracy in positioning.
3.2. CONTROL SEGMENT
The control or ground segment of the GPS consists of unmanned monitor stations located around the world(Hawaii and Kwajalein in the Pacific Ocean; Diego Garcia in the Indian Ocean; Ascension Island in the Atlantic Ocean; and Colorado Springs, Colorado). The GPS Master Control Station (MCS) is located on the Falcon Air Force Base in Colorado. The monitoring stations track any GPS satellites in view and collect ranging information from the radio broadcast of each viewable satellite. As information is collected it is sent back to master control for processing. Master control uses this data to create a navigation message containing precise orbit positions, time adjustments, and system parameters. Monitoring stations with uplink capabilities can then transmit the navigation message back up to the appropriate GPS satellite. Subsets of this navigation message are rebroadcast for use by receiving equipment.
3.3 USER SEGMENT
The user segment consists of the appropriate antenna, receiver, and processor used to gain access to GPS. With this equipment a user's can receive GPS transmissions and compute their precise position, velocity, and time. This segment includes a variety of products used for different applications: marine navigation, map surveying, tracking vehicles, search and rescue, and many others.
3.3.1 SPS - Standard Positioning Service
Standard Positioning Service (SPS) is a free service available to civilian users of GPS. SPS is broadcast from the GPS constellation as C/A-code on the L1 frequency. It is designed around a limited standard of position and timing accuracy that is available to worldwide users without restrictions. The accuracy (and the intentional degradation through selective availability) of SPS is established by the U.S. Department of Defense based on national security interest. Accuracy of SPS was initially designed to be within 100 horizontal meters. Changes in consumer end receiver-processing technology, however, have increased the degree of accuracy that can be achieved with SPS.
3.3.2 PPS - Precise Positioning Service
Because of it's greater accuracy the Precise Positioning Service (PPS) is available only to U.S. and allied military, some U.S. Government agencies, and authorized civilian users. Cryptographic equipment and keys and specially equipped receivers are needed for use of the PPS. Horizontal accuracy is predictable to 22 meters.
4. TRILATERATION-THE WORKING PRINCIPLE OF OPERATION
A GPS receiver's job is to locate four or more of these satellites, figure out the distance to each, and use this information to deduce its own location. This operation is based on a simple mathematical principle called trilateration. Trilateration is based on the fact that a body cannot occupy two positions in space simultaneously. Trilateration can be done in two ways
2-D Trilateration
3-DTrilateration
4.2. 2-D TRILATERATION
If an object is 625 miles from A it could be anywhere on a circle around A that has a radius of 625 miles.
And if the object is 690 miles from B and this information is combined with the former information, we have two circles that intersect to get the position which results in two positions And with a third information we can clearly spot the exact position
This same concept works in three-dimensional Space, as well, but has spheres instead of circles
.
4.3. 3-D TRILATERATION
Fundamentally, three-dimensional trilateration isn't much different from two-dimensional trilateration, but it's a little trickier to visualize. Imagine the radii from the examples in the last section going off in all directions. So instead of a series of circles, you get a series of spheres.
If a person know he is 10 miles from satellite A in the sky, he could be anywhere on the surface of a huge, imaginary sphere with a 10-mile radius. If he also knows he is 15 miles from satellite B he can overlap the first sphere with another, larger sphere. The spheres intersect in a perfect circle. If he knows the distance to a third satellite, he gets the third sphere, which intersects with this circle at two points.
The Earth itself can act as a fourth sphere -- only one of the two possible points will actually be on the surface of the planet, so you can eliminate the one in space. Receivers generally look to four or more satellites, however, to improve accuracy and provide precise altitude information.
In order to make this simple calculation, then, the GPS receiver has to know two things:
¢ The location of at least three satellites above him
¢ The distance between he and each of those satellites
The GPS receiver figures both of these things out by analyzing high-frequency, low-power radio signals from the GPS satellites. Better units have multiple receivers, so they can pick up signals from several satellites simultaneously.
Radio waves are electromagnetic energy, which means they travel at the speed of light (about 186,000 miles per second, 300,000 km per second in a vacuum). The receiver can figure out how far the signal has traveled by timing how long it took the signal to arrive.
5 MEASURING DISTANCE
1. Distance to a satellite is determined by measuring how long a radio signal takes to reach us from that satellite.
2. To make the measurement we assume that both the satellite and our receiver are generating the same pseudo-random codes at exactly the same time.
3. By comparing how late the satellite's pseudo-random code appears compared to our receiver's code, we determine how long it took to reach us.
4. Multiply that travel time by the speed of light and you've got distance.
At a particular time, the satellite begins transmitting a long, digital pattern called a pseudo-random code. The receiver begins running the same digital pattern also exactly at midnight. When the satellite's signal reaches the receiver, its transmission of the pattern will lag a bit behind the receiver's playing of the pattern.
The length of the delay is equal to the signal's travel time. The receiver multiplies this time by the speed of light to determine how far the signal traveled. Assuming the signal traveled in a straight line, this is the distance from receiver to satellite.
In order to make this measurement, the receiver and satellite both need clocks that can be synchronized down to the nanosecond. To make a satellite positioning system using only synchronized clocks, you would need to have atomic clocks not only on all the satellites, but also in the receiver itself. But atomic clocks cost are too expensive for everyday consumer use.
The Global Positioning System has a clever, effective solution to this problem. Every satellite contains an expensive atomic clock, but the receiver itself uses an ordinary quartz clock, which it constantly resets. In a nutshell, the receiver looks at incoming signals from four or more satellites and gauges its own inaccuracy.
6. SOURCES OF GPS MEASUREMENT ERRORS
Ideally, GPS receivers would easily be able to convert the C/A and P(Y)-code measurements into accurate positions. However, a system with such complexity leaves many openings for errors to affect the measurements. The following are several causes of error in GPS measurements.
6.1. Clocks
Both GPS satellites and receivers are prone to timing errors. Satellites often possess cesium atomic clocks. Ground stations throughout the world monitor the satellites to ensure that the atomic clocks are accurate. Receiver clock error is unknown and often depends on the oscillator provided within the unit. However, it can be calculated and then eliminated once the receiver is tracking at least four satellites.
6.2 Ionosphere
The ionosphere is one of the leading causes of GPS error. The speed of light varies due to atmospheric conditions. As a result, errors greater than 10 meters may arise. To compensate for these errors, the second frequency band L2 was provided. By comparing the phase difference between the L1 and L2 signals, the error caused by the ionosphere can be calculated and eliminated.
6.3 Multi path
The antenna receives not only direct GPS signals, but also multi path signals: reflections of the radio signals off the ground and/or surrounding structures (buildings, canyon walls, etc). For long multi path signals, the receiver itself can filter the signals out. For shorter multipath signals that result from reflections from the ground, special antenna features may be used such as a ground plane, or a choke ring antenna. Shorter multipath signals from ground reflections can often be very close to the direct signals, and can greatly reduce precision.
6.4 Selective availability
In the past, the civilian signal was degraded, and a more accurate Precise Positioning Service was available only to the United States military, its allies and other, mostly government users. However, on May 1, 2000, then US President Bill Clinton announced that this "Selective Availability" would be turned off, and so now all users enjoy nearly the same level of access, allowing a precision of position determination of less than 20 meters.
7.TECHNIQUES TO IMPROVE GPS ACCURACY
Even if there are many problems pertaining to accuracy due to errors in measurement, the accuracy of GPS can be improved in a number of ways:
7.1. Differential GPS (DGPS)
DGPS helps correct these errors. The basic idea is to gauge GPS inaccuracy at a stationary receiver station with a known location. Since the DGPS hardware at the station already knows its own position, it can easily calculate its receiver's inaccuracy. The station then broadcasts a radio signal to all DGPS-equipped receivers in the area, providing signal correction information for that area. In general, access to this correction information makes DGPS receivers much more accurate than ordinary receivers.
Differential correction techniques are used to enhance the quality of location data gathered using global positioning system (GPS) receivers. Differential correction can be applied in real-time directly in the field or when post processing data in the office. Although both methods are based on the same underlying principles, each accesses different data sources and achieves different levels of accuracy. Combining both methods provides flexibility during data collection and improves data integrity.
The underlying premise of differential GPS (DGPS) is that any two receivers that are relatively close together will experience similar atmospheric errors. DGPS requires that a GPS receiver be set up on a precisely known location. This GPS receiver is the base or reference station. The base station receiver calculates its position based on satellite signals and compares this location to the known location. The difference is applied to the GPS data recorded by the second GPS receiver, which is known as the roving receiver. The corrected information can be applied to data from the roving receiver in real time in the field using radio signals or through post processing after data capture using special processing software.
7.2. Exploitation of DGPS for Guidance Enhancement (EDGE)
EDGE is an effort to integrate DGPS into precision guided munitions such as the Joint Direct Attack Munition (JDAM).
7.3. The Wide-Area Augmentation System (WAAS).
Wide Area Augmentation System is the latest method of providing better accuracy from the GPS constellation. It is similar in principle the DGPS capability that is built into all Garmin and many other units except that a second receiver is not required. Instead of a beacon receiver the correction data is sent via a geo-stationary satellite and is decoded by one of the regular channels already present in the GPS receiver. Thus one of the 12 channels can be designated to decode regular GPS signals or can be used to decode the WAAS data. Actually, as currently implemented, when WAAS is enabled two channels will be dedicated to WAAS. While WAAS is the name of the implementation of this technology in the US the system is intended for worldwide use. The generic name for WAAS is SBAS (Space Based Augmentation System) or WADGPS (Wide Area Differential GPS).
The way this works is that a set of ground stations all over the US collect correction data relative to the area of the country they are located in. The entire data is then packaged together, analyzed, converted to a set of correction data by a master station and then uploaded to the geo-stationary satellite, which in turn transmits the data down to the local GPS receiver. The GPS receiver then figures out which data is applicable to its current location and then applies the appropriate corrections to the receiver. Similar systems are being set up in other areas of the world but they are not ye In addition to correction information the ground stations can also identify a GPS satellite that is not working within specification thereby improving the integrity of the system for aviation use.
7.4. A Local-Area Augmentation System (LAAS).
This is similar to WAAS, in that similar correction data are used. But in this case, the correction data are transmitted from a local source, typically at an airport or another location where accurate positioning is needed. These correction data are typically useful for only about a thirty to fifty kilometer radius around the transmitter.
7.5. Wide Area GPS Enhancement (WAGE)
WAGE is an attempt to improve GPS accuracy by providing more accurate satellite clock and ephemeris (orbital) data to specially-equipped receivers.
7.6. Relative Kinematic Positioning (RKP)
RKP is another approach for a precise GPS-based positioning system. In this approach, accurate determinination of range signal can be resolved to an accuracy of less than 10 centimeters. This is done by resolving number of cycles in which the signal is transmitted and received by the receiver. This can be accomplished by using a combination of differential GPS (DGPS) correction data, transmitting GPS signal phase information and ambiguity resolution techniques via statistical tests - possibly with processing in real-time (real-time kinematic positioning
8. APPLICATIONS
8.1. Military
Army people were the first to use and they themselves are the intensive users. Their use is incommensurable
8.1.1. Guidance
The primary military purpose is to allow improved command and control of forces through an enhanced ability to accurately specify target locations for cruise missiles or troops. The satellites also carry nuclear detonation detectors.
For example U.S. Marines used GPS-guided parachutes to carry supplies to soldiers in an Iraq combat zone for the first time on August 9.
8.1.2 GPS jamming
A large part of modern munitions, the so-called "smart bombs" or precision-guided munitions, use GPS. GPS jammers are available, from Russia, and are about the size of a cigarette box. The U.S. government believes that such jammers were used occasionally during the U.S. invasion of Afghanistan. Some officials believe that jammers could be used to attract the precision-guided munitions towards noncombatant infrastructure; other officials believe that the jammers are completely ineffective. In either case, the jammers are attractive targets for anti-radiation missiles
8.2 Air
GPS offers an inexpensive and reliable supplement to existing navigation techniques for aircraft. Civil aircraft typically fly from one ground beacon, or waypoint, to another. With GPS, an aircraft's computers can be programmed to fly a direct route to a destination. The savings in fuel and time can be significant.
GPS can simplify and improve the method of guiding planes to a safe landing, especially in poor weather. With advanced GPS systems, airplanes can be guided to touchdown even when visibility is poor. For the private pilot, inexpensive GPS systems provide position information in a practical, simple, and useful form.
8.2.1. GPS Navigation in the Air
Pilots on long distance flights without GPS rely on navigational beacons located across the country. Using GPS, aircraft can fly the most direct routes between airports.
8.2.2. GPS in the Cockpit
Pilots often rely on GPS to navigate to their destinations. A GPS receiver in the cockpit provides the pilot with accurate position data and helps him or her keep the airplane on course.
8.3. Sea
8.3.1 Nautical Chart Error
The data collected from satellite navigation systems provide more accurate information for maps and nautical and aeronautical charts. This example demonstrates how charts are updated to prevent navigational mishaps.
GPS is a powerful tool that can save a ship's navigator hours of celestial observation and calculation. GPS has improved efficient routing of vessels and enhanced safety at sea by making it possible to report a precise position to rescuers when disaster strikes.
GPS improves efficiency on land as well. Delivery trucks can receive GPS signals and instantly transmit their position to a central dispatcher. Police and fire departments can use GPS to dispatch their vehicles efficiently, reducing response time. GPS helps motorists find their way by showing their position and intended route on dashboard displays. Railroads are using GPS technology to replace older, maintenance-intensive mechanical signals
8.4 Land
8.4.1. GPS in Vehicles
Many types of GPS systems can be used on vehicles, providing the driver with the current position and a local map.
8.4.2 Mapping the Earth
Surveyors and map makers use GPS for precision positioning. GPS is often used to map the location of such facilities as telephone poles, sewer lines, and fire hydrants. Surveyors use GPS to map construction sites and property lines. Forestry, mineral exploration, and wildlife habitat management all use GPS to precisely define positions of important assets and to identify changes.
During data collection, GPS points can be assigned codes to identify them as roads, streams, or other objects. These data can then be compared and analyzed in computer programs called Geographic Information Systems (GIS).
8.4.3 Surveying With GPS
Surveying that previously required hours or even days using conventional methods can be done in minutes with GPS.
8.4.4 Set Your Watch
Because GPS includes a very accurate time reference, the system is also widely used for timekeeping. GPS receivers can display time accurate to within 150 billionths of a second.
8.4.5 Managing the Land
The use of GPS is widespread in field that require geospatial information for managing assets over large areas. Forestry, mineral exploration, and wildlife habitat management all use GPS to precisely define positions of important assets and to identify changes.
8.4.6 GPS and Agriculture
GPS receivers installed in farm equipment provide accurate position information. This enables farmers to apply fertilizers and harvest crops with great precision.
8.4.7 Yield Map
Maps of crop yield can be made using agricultural GPS systems. The map shown here indicates how crop yield varies across a field. These maps can be created during harvesting, allowing farmers to accurately plan how the fields should be used and fertilized for future crops.
8.4.8 New Frontiers in Science
GPS has made scientific field studies throughout the world more accurate and has allowed scientists to perform new types of geographic analyses. Geologists use GPS to measure expansion of volcanoes and movement along fault lines. Ecologists can use GPS to map differences in a forest canopy. Biologists can track animals using radio collars that transmit GPS data. Geographers use GPS to define spatial relationships between features of the Earth's surface.
8.4.9 GPS at the Smithsonian
Scientific applications of GPS at the Smithsonian range from regional scale mapping to site-specific surveys. Scientists can use GPS to locate sites within satellite images to help them understand the regional environment. GPS can also be used in documenting specimens collected in the field. In the past, it was often not possible to accurately record the location of collection sites. Smithsonian scientists now use GPS receivers to quickly and accurately identify specimen locations.
8.4.10 Science in the Field
Scientists use GPS for a wide range of applications. Scientific analysis that formerly had to be conducted in a laboratory can now be done quicker and easier in the field.
8.4.11 Research
Scientific applications of GPS at the Smithsonian range from regional scale mapping to site-specific surveys. Scientists can use GPS to locate sites within satellite images to help them understand the regional environment. GPS can also be used in documenting specimens collected in the field. In the past, it was often not possible to accurately record the location of collection sites. Smithsonian scientists now use GPS receivers to quickly and accurately identify specimen locations.
8.5 Applications in India
8.5.1 Architecture
GPS is used in architectural sitings. When used with 3D modeling, GPS provides a more realistic context for architectural design.
8.5.2 E-Commerce
Conducting research to develop secure transactions using GPS. The system would feature real-time information on users as well as applications to reduce user fears of computer "hacking."
8.5.3 Education
GPS is used to track transmission and power line distribution network inspections, track container movements, and map the location of ground water sources and pollution
8.5.4 Geographic Information Systems
The satellite IRS-1D will be launched from Sriharikota on September 29, 1997. One of the experimental units on IRS-1D is a 4.15-kg Satellite Position System. Using the Global Positioning System receiver on the satellite, the SPS will determine the position of the satellite in orbit.
8.5.5 Development of GPS receivers
India has begun to manufacture Global Positioning System receivers, in a project funded by the Department of Electronics and the Defence Research Development Organization. These receivers are up to the highest standards at half the imported cost. The Indian-made receivers are being used commercially by boat owners and some military vehicles and
aircraft. buses in the south Indian city of Bangalore are running on time thanks to the constellation of Global Positioning System (GPS) navigation.. Receivers built by Bangalore's based Bharat Electrical Ltd., were mounted on 200 of the city's 2,300 buses in a pilot project about a year ago. The program is helping ensure that the buses remain on schedule and make all their designated stops. The receivers continuously record each bus' coordinates, which are converted by software into locations identifiable by known landmarks every 200 meters along the bus route. The receivers are able to store 3 days of recordings to produce a record of the scheduled performance. This system has helped identify missed trips and catch speeding drivers
8.5.6 Infrastructure Development
The Highway Automation System is a project that plans to page link the Indian road and communication infrastructure. The idea for HAS came from the global positioning system. Electronic kiosks will be set every 50 km on the highways and the vehicles will have an electronic monitoring device. Truck operators will be the first users of HAS.
8.5.7 Mining & Construction
The Minister of State for Coal, Dilip Ray, would like to increase the use of GPS technology to locate new mineral resources, improve scientific planning for the exploitation of natural resources, and better management systems. He said that GPS is already being used in many areas of coal mining.
8.5.8 Surveying & Mapping
Beginning in April 1994, one of the largest, deepest pipeline routes was mapped. This was possible using differential global positioning system to calculate the position of the tow fish from the ship, which was usually 200-m ahead. The pipeline that was laid was 24-in. for 700 miles at depths in the Arabian Sea to 3,500 m.
GPS has been extensively used in Delhi - Utility Mapping Project. For photogrammatry work GPS Control Grid Network covering an area of 1600 sq.km has been established with about 500 gps control point at every 3-5 km on ground. The GPS control grid network project will be completed by May 2000 covering entire Delhi
Vehicle Location
We want to deploy the GPS network in almost the whole country so that we can provide tracking systems not only for vehicle position but other parameters of the vehicle such as remaining fuel, speed, hazard warnings, and predefined messages. All these things have to be monitored remotely.
We are using GPS technology for monitoring and hence for optimum use of highly costly HEMMs in mines so as to increase the productivity. Also we are monitoring health of these HEMMs by making interface with Engine Monitoring System of these equipments. The performance of operators is monitored online. Payment of vendors, OEM suppliers is based on the report generated by the system. GPS is playing an important role.
Auto car team embarks on K2K-II expedition: From Kutch to Kivithoo. New Delhi: Auto car India, a leading automobile magazine, set out on a expedition from the western most point of the country (Kutch) to the eastern tip(Kivithoo) on February 1, 2003 with the objective of mapping the entire route, kilometer by kilometer. K2K was also undertaken in a bid to map the country's road conditions from the northern most point to the southern most point. This year the team completed the voyage from Koteshwar in Kutch (Gujarat) to Kivithoo in Arunachal Pradesh.
Civic body installs GPS in conservancy trucks:
Twelve Dumper placers and 16 corporation conservancy lorries might soon have Global Positioning System (GPS) instruments in place.
A review of the performance of the Global Positioning System (GPS), on four dumper placer trucks of the Coimbatore Corporation, has been found to be effective in tracking vehicles. Consequently, the civic body has decided to install it in more vehicles engaged in conservancy operations.
As a test case, the Corporation had installed the GPS in four of its 16 dumper placers in an effort at finding out whether the technology could help ensure transparency in waste disposal. The 'passive vehicle tracking system' had recorded the entire trip of each dumper placer. A private institution that had developed the GPS provided the monitoring office at the Corporation a 'TripMapp' software and a geo reference city map, containing the names of all the roads/streets and the waste dump locations across the city.
A trip summary was downloaded from the GPS in one of the trucks on Tuesday to review its performance and also to check whether there were any route diversions. It was found that the GPS fulfilled the requirements of the Corporation and hence it had been decided to installs 12 more dumpers and Lorries with the GPS
9 CONCLUSION
The digital revolution combined with the progressing communication theory brought tremendous advancements in information revolution. Even if there are problems with the present GPS system it offers a credible service to both high end and low end users. There are also a variety of techniques available to correct the pitfalls. As of now the present research in the field is to reduce the cost, increase the accuracy. It also aims at reducing the weight and to clear the line of sight between GPS receiver and four satellites. Satellite based navigational aid
¢ Guide by 24 satellites round the globe in 6 orbits
¢ 3D positioning and time
¢ Type of terrain and weather does not effect positioning
¢ Cheap and precise operating equipment
¢ Inherent error correction mode
¢ A variant of GPS , DGPS has already been introduced
10 REFERENCES
¢ GIS and Remote Sensing Applications in Environmental Management (Indian Institute of Science, Bangalore)
¢ wikipedia.com
¢ Trimble™s online GPS tutorial
¢ howstuffworks.com
