Introduction to Satellite PositioningSatellite Positioning [gloss.] is a modern technique developed towards the end of the 20th century, and was pioneered by the USA and Russia. The USA system is referred to as the Global Positioning System (GPS) [gloss.] , and provides a highly precise method of determining the position of almost any object on the earth or within the atmosphere. Much research work is on-going in this field, and the applications and uses of GPS are numerous.
Basic Introduction to GPS Satellite PositioningGPS works by having satellites, of which there were 24 initially, orbiting the earth in roughly 12-hour periods. Each satellite, which is solar-powered, transmits a signal to receivers on the Earth. The theory is that any receiver can pick up at least 4 of these signals from different satellites, and through trigonometry deduce its position with high accuracy. How precise the location is will depend on many things, such as the quality of the receiver, environmental and atmospheric conditions, observation type and time of day. Simple hand-held, or in-car, receivers typically give an accuracy of 5 - 10m. More precise survey grade receivers, and processing techniques can increase accuracy to within millimetres.
You will learn lots more about the maths behind GPS in the second and third year Surveying modules on the course, but to find out more visit the American National Air and Space Museum site (www.nasm.si.edu/galleries/gps/work.html).
Alternatively, for a more technical background, visit the Institute of Engineering Surveying and Space Geodesy (www.nottingham.ac.uk/iessg/isglinks.html).
GalileoThis is the European answer to GPS (GPS was set up and is run by the Americans). With satellite launching underway, the satellites are due to be fully operational by 2008. Check out the European Space Agency's official web-site for further details (www.esa.int/export/esaSA/GGGMX650NDC_navigation_0.html).
Uses and Applications of Satellite PositioningUntil recently, the US military deliberately down-graded the precision of the GPS through a process known as Selective Availability (SA), so that civilian users, using the hand-held receivers would have a lower level of accuracy, for reasons of security. This has now been stopped, and all users can obtain accurate details of their position. SA did not affect users of the survey-grade GPS.
Uses for general navigation and finding co-ordinates of places are clearly obvious. Within civil engineering it is starting to be used for surveying work, more about this can be learned from the 1st year Surveying and Management 1 module.
Within this module, we are looking at ways in which satellite positioning can be used in the transport field, and there is much research work on-going in this area.
Traditional Applications in TransportA satellite positioning system, such as GPS, can provide many uses when used as a stand-alone unit. A GPS receiver in a car, which is not uncommon these days, can calculate the car's position and then reference this to a database with the road network on, to show the driver his/her location. The basic car 'sat-nav' system will be able to plan a route and provide visual/aural instructions on which route to take, simply by using the GPS information and an electronic map.
As GPS technology develops, further uses are being found, including:
New applications of GPS and ITS are being developed all the time so keep a look out for any recent developments.
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