Gps

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A short summary about how GPS works and references to "key" parts of this system.

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  • Most people know what is this, even an increasing group have one of them. Sometimes it can be amazing and overwhelming to consider the way that technology has changed our lives. Before that, we would have to rely on paper maps to guide us along our journeys, now we have a little electronic device that will talk to us as we drive.
  • Although weather conditions it isn’t a problem to this systems, we will see that it’s affected by other external agents
  • This position can then be displayed usually with a moving map display. Many GPS units also show derived information such as direction and speed, calculated from position changes.
  • Ground stations provides information used to maintain sync the satellite segment.
  • The satellite orbits are roughly 25,000 kilometres from the earth's centre, or 20,000 kms above the earth's surface. As of March of this year, there are 31 actively broadcasting satellites (7 in spare) in the GPS constellation , and two older, retired from active service satellites kept in the constellation as orbital spares. The additional satellites improve the precision of GPS receiver calculations by providing redundant measurements If you do the math, that's about 2.6 kilometers per second.
  • A GPS receiver's job is to locate six or more of satellites, figure out the distance to each, and use this information to deduce its own location. In order to make this calculation, the GPS receiver has to know two things: The location of at least three satellites above you The distance between you and each of those satellites There are a lot of receptors
  • The first mobile phone which was able to connect with GPS network was launched in the late 1990’s ->Gemonates.. I don't know if I will repent
  • GPS system is based on WGS (World Geodetic System – 1984), an extension from NAD83. A Datum is a known surface (usually a ellipsoid) which is used to describe the location of unknown points on the earth. Since these can have different radii and centre points, same point in the Earth can have quite different coordinates depending on the datum used to make the measurement. An Example of differences between 2 datums.
  • If you are working in a construction project, pay attention on which DATUM are you using, because otherwise… Referencing coordinates to the wrong datum can result in position errors of hundreds of meters…
  • Gps

    1. 1. GPS Global Positioning System Alejandro Barrera
    2. 2. ¿What is GPS? INTRODUCTION  Is a space-based global navigation satellite system , developed by U.S. Navy around 1970. GPS has become a widely used aid to navigation worldwide, and a useful tool for map-making, land surveying (a topography branch to delimit surfaces ), commerce, scientific uses, tracking and hobbies such as geocaching and waymarking.
    3. 3. GPS - Introduction It provides reliable positioning, navigation, and timing services to worldwide users on a continuous basis in all weather, day and night, anywhere on the Earth.
    4. 4. GPS - ¿How it works? GPS is the acronym for Global Positioning System. GPS consists of a series of satellites (24+) that transmit data that allow receivers on Earth to determine their location with great accuracy. Also included in this system are ground stations (5) that are used for detecting and updating errors. Generally we only think about the receivers and call those a GPS or GPS units.
    5. 5. GPS - ¿How it works? II <ul><li>A GPS receiver calculates its position by precisely timing the signals sent by the GPS satellites above the Earth. Each satellite continually transmits messages which include the time the message was sent and some additional information. 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. </li></ul>next
    6. 6. GPS - Trilateration Trilateration is a method for determining the intersections of three sphere surfaces given the centers and radii of the three spheres BACK
    7. 7. GPS - Components satellites receivers ground station to continue
    8. 8. Satellites 24 (+ spare) earth-orbiting satellites – at least 6 are always in the line of sight, up to 12 at any one time (thus 12 channel receivers) GPS - Components BACK <ul><li>They are located into 6 orbital planes separated by 60°. each satellite makes two complete orbits each day. </li></ul>
    9. 9. from 80€ to 600€ you can find devices with features as electronic compass or barometric altimeter and improvements like better accuracy or long battery life. GPS - Components Receivers
    10. 10. Nowadays, lots labels offer mobile phones with a GPS antenna integrated (Nokia, Samsung, Apple iPhone,…) and everybody can download a GPS software and use it. GPS - Components Receivers II BACK
    11. 11. GPS - Datums <ul><li>Datum </li></ul><ul><ul><li>NAD27, NAD83, WGS84 </li></ul></ul>
    12. 12. GPS - Datums II
    13. 13. The End

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