GPSGPSGlobal Global PositioningPositioning SystemSystem

Alejandro Barrera

¿What is GPS?¿What is GPS?INTRODUCTIONINTRODUCTION

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.

GPS - IntroductionGPS - 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.

GPS - ¿How it works?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.

GPS - ¿How it works? IIGPS - ¿How it works? II•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.

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GPS - TrilaterationGPS - Trilateration

Trilateration is a method for determining the intersections of three sphere surfaces given the centers and radii of the three spheres

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GPS - ComponentsGPS - Components

satellites

receivers

ground station

to continue

SatellitesSatellites

24 (+ spare) earth-24 (+ spare) earth-orbiting satellites – at orbiting satellites – at least 6 are always in the least 6 are always in the line of sight, up to 12 at line of sight, up to 12 at any one time (thus 12 any one time (thus 12 channel receivers)channel receivers)

GPS - ComponentsGPS - Components

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• They are located into 6 orbital planes separated by 60°. each satellite makes two complete orbits each day.

from 80€ to from 80€ to 600€ you can 600€ you can find devices find devices with features with features as as electronic electronic compasscompass or or barometric barometric

altimeter and altimeter and improvements improvements

like betterlike better accuracy or accuracy or long battery long battery

life.life.

GPS - ComponentsGPS - ComponentsReceiversReceivers

Nowadays, lots labels Nowadays, lots labels offer mobile phones offer mobile phones with a GPS antenna with a GPS antenna integrated (Nokia, integrated (Nokia, Samsung, Apple Samsung, Apple iPhone,…) and iPhone,…) and everybody can everybody can download a GPS download a GPS software and use it.software and use it.

GPS - ComponentsGPS - ComponentsReceivers IIReceivers II

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GPS - DatumsGPS - Datums• Datum

– NAD27, NAD83, WGS84

GPS - Datums IIGPS - Datums II

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