The GPS/WAAS System Department of Science and Space Technology OPTION : GNSS Presented by : ANOUSSOUNGOUME A. F. NABEINA BASSOUNG M. A. Flore Under the.

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Présentation au sujet: "The GPS/WAAS System Department of Science and Space Technology OPTION : GNSS Presented by : ANOUSSOUNGOUME A. F. NABEINA BASSOUNG M. A. Flore Under the."— Transcription de la présentation:

1 The GPS/WAAS System Department of Science and Space Technology OPTION : GNSS Presented by : ANOUSSOUNGOUME A. F. NABEINA BASSOUNG M. A. Flore Under the direction of : Pr JAMAL Eddine ACADEMIC YEAR : 2018 – 2019

2 PLAN INTRODUCTION GPS: Historical, Architecture and Functions WAAS: Historical, Services and Applications WAAS ARCHITECTURE WAAS OPERATION CONCLUSION AND PERSPECTIVES

3 INTRODUCTION

4 GNSSGPSFLAWSWAAS

5 GPS (Global Positionning System)

6 Satellite navigation systems that were initially used by military services are now used in a number of areas: Road, air and marine Civil engineering; Topography; Agriculture… Let's talk about the US GPS and its WAAS augmentation system. INTRODUCTION GPS ARCHITECTURE AND OPERATION HISORICAL Of GPS HISORICAL Of GPS

7 HISORICAL Of GPS After the Second World War, the Cold War between the USA and the USSR led these two countries to conquer space in order to take control of the world. 4 October 1957, the first artificial satellite (Sputnik1) has been put into orbit by the USSR. 29 July 1958,Creation of NASA (National Aeronautics and Space Administration) Between 1978 and 1985, 11 satellites of the Block I were put into orbit. Between 1989 and 2017, 61 satellites of the Block II equipped with 2 or 3 atomic clocks were put into orbit. From 2018, 10 satellites of the Block III were put into orbit. They emit a new civil signal (L1C) on the L1 frequency. INTRODUCTION GPS ARCHITECTURE AND OPERATION HISORICAL Of GPS HISORICAL Of GPS

8 GPS ARCHITECTURE AND FUNCTIONS Architecture Ground Segment Space Segment User Segment There are 38 extended reference stations in North America and the United States, including Alaska and Puerto Rico. The basic constellation of Global Positioning System (GPS) consists of 24 locations on six aircraft, with four locations per aircraft. The GPS constellation has 30 operational satellites broadcasting reliable information. It brings together all users in navigation; agriculture; topography; … INTRODUCTION GPS ARCHITECTURE AND OPERATION HISORICAL Of GPS HISORICAL Of GPS

9 GPS ARCHITECTURE AND FUNCTIONS  Ground Segment The GPS stations are 5 in thewold and all belong to theAmerican government. The main base is Colorado Springs. The 4 others are distributed in the various oceans as you can see on picture. INTRODUCTION GPS ARCHITECTURE AND OPERATION HISORICAL Of GPS HISORICAL Of GPS

10  Space Segment The GPS includes at least 24 satellites traveling at an altitude of 20,200 km. They are divided into 6 separate orbits at the rate of 4 satellites per orbit. GPS ARCHITECTURE AND OPERATION INTRODUCTION GPS ARCHITECTURE AND OPERATION HISORICAL Of GPS HISORICAL Of GPS

11  User Segment It is formed by GPS receivers, which receive, decode and process the signals emitted by satellites. It brings together all users users in navigation; agriculture; topography; … GPS ARCHITECTURE AND OPERATION INTRODUCTION GPS ARCHITECTURE AND OPERATION HISORICAL Of GPS HISORICAL Of GPS

12 GPS OPERATION: SIGNALS The GPS satellites transmit two low power radio signals, indicated L1 and L2. The civilian GPS uses the L1 frequency of 1575.42 megahertz in the UHF band. A GPS signal contains three different bits of data: pseudo-random code, ephemeris data, and almanac data:  The pseudo-random code is simply an identification code that identifies which satellite transmits the information.  Ephemeris data tells the GPS receiver where each GPS satellite should be at all times throughout the day.  The almanac data, which are constantly transmitted by each satellite, contains important information on the status of the satellite (good or bad), the date of the day and the time. INTRODUCTION GPS ARCHITECTURE AND OPERATION HISORICAL Of GPS HISORICAL Of GPS

13 GPS LIMIT The difficulties of GPS are related to accuracy, which depends on the following factors: Propagation medium (ionosphere, troposphere, multi-path, interference) Satellite atomic clock drifts: ephemeral errors, clock degradation All these factors lead to a geometric dilution of the accuracy from 100 m to 150 m. The WAAS augmentation system was implemented with the aim of improving the accuracy and fulfilling the integrity, continuity and availability of GPS. INTRODUCTION GPS ARCHITECTURE AND OPERATION HISORICAL Of GPS HISORICAL Of GPS

14 WAAS (Wide Area Augmentation System)

15 INTRODUCTION HISTORICAL ARCHITECTURE OPERATION CONCLUSION AND PERSPECTIVES SERVICES AND APPLICATIONS

16 HISTORICAL INTRODUCTION HISTORICAL ARCHITECTURE OPERATION CONCLUSION AND PERSPECTIVES SERVICES AND APPLICATIONS  1995: Creating the WAAS system  1996-1997 : Establishment of WAAS logistics resources  1999 : Date of issue of the first WAAS test signal  2003 : the year the WAAS system was first used for a commercial flight using a WAAS-GPS receiver  2007 : start of correction message transmission certified by the GLAXY 15 satellite  2008 : the system extends its coverage area by setting up new stations in the Mexico and Canada

17 INTRODUCTION HISTORICAL ARCHITECTURE OPERATION CONCLUSION AND PERSPECTIVES SERVICES AND APPLICATIONS Services Precision Integrity availability WAAS improves the accuracy of GPS to meet the basic requirements of navigation. WAAS provides important integrity information across the entire GPS constellation WAAS improves system availability through the use of geostationary communication satellites (GEOs) carrying navigational payloads

18 INTRODUCTION HISTORICAL ARCHITECTURE OPERATION CONCLUSION AND PERSPECTIVES SERVICES AND APPLICATIONS Applications The applications of the GPS-WAAS system concern the positioning of fixed points (field of geodesy and topography), the positioning of mobile points (main area of navigation, maritime transport and road transport). In addition, the ultra-precise diffusion of time by the system opens applications in the field of metrology. In the field of geodesy, we note: the work of monitoring and deformation of the earth's crust, displacement of tectonic plates, widening of seismic faults, continental drift and the detection of subsidence.

19 INTRODUCTION HISTORICAL ARCHITECTURE OPERATION CONCLUSION AND PERSPECTIVES SERVICES AND APPLICATIONS WMS WRS GPS receivers Satellite GEO Architecture Ground Segment User Segment Space segment GUS WAAS receivers 3 GEOWAAS 38 Stations 2 control centers

20 OPERATION Receipt of GPS signals by WRS Explanation INTRODUCTION HISTORICAL ARCHITECTURE OPERATION CONCLUSION AND PERSPECTIVES SERVICES AND APPLICATIONS GPS satellite signals are received via the NAS (National Airspace System) at many widely spaced Wide Area Reference Station (WRS) sites. The WRS slots are precisely raised so that any errors in the received GPS signals can be detected. The difference is instead of using the signal travel time to calculate the position, the reference stations use their known position to calculate the timing. Since the reference stations know exactly where they are, they can figure out what the signal path period should be. They then compare the calculated times to the real times. The difference is an "error correction" factor.

21 OPERATION Sending information collected by WRS to WMS Explanation INTRODUCTION HISTORICAL ARCHITECTURE OPERATION CONCLUSION AND PERSPECTIVES CONCLUSION AND PERSPECTIVES SERVICES AND APPLICATIONS Envoi At the WMS, WAAS augmentation messages are generated. These messages contain information that allows GPS receivers to eliminate errors in the GPS signal, allowing a significant increase in the accuracy and reliability of the location.

22 OPERATION Sends WMS-corrected message to GUS and then transfers information to GEO WAAS Explanation INTRODUCTION HISTORICAL ARCHITECTURE OPERATION CONCLUSION AND PERSPECTIVES SERVICES AND APPLICATIONS The augmentation messages are sent from the WMS to the uplink stations to be transmitted to the navigation payloads of the geostationary communications satellites. The corrected differential message is then sent by these GEO WAAS satellites. The information is compatible with the basic structure of the GPS signal, which means that any WAAS GPS receiver can read the signal. WAAS

23 OPERATION Dissemination of information obtained by GEO WAAS to aircraft Explanation INTRODUCTION HISTORICAL ARCHITECTURE OPERATION CONCLUSION AND PERSPECTIVES SERVICES AND APPLICATIONS The useful navigation data broadcast the augmentation messages on a GPS signal. The GPS / WAAS receiver processes the WAAS augmentation message as part of the position estimation. The GPS signal of the navigation transponder can also be used by the receiver as an additional source for calculating the user's position.

24 SIGNAL WAAS INTRODUCTION HISTORICAL ARCHITECTURE OPERATION CONCLUSION AND PERSPECTIVES SERVICES AND APPLICATIONS At the GEOWASS level, three signals are transmitted:  GEO Ranging: transmitting L1 GPS type signals from GEO satellites to increase the number of navigation satellites available to users.  Wide Area Differential (WAD): differential corrections of existing GPS and GEO navigation services calculated in an extended area to improve the performance of navigation services. This includes corrections to orbits and satellite clocks, as well as information to estimate the delay in the signal as it passes through the ionosphere.  GNSS / Ground Integrity Channel (GIC): Integrity information to inform the availability of GPS and GEO secure navigation services.

25 CONCLUSION AND PERSPECTIVES The purpose of this report was to introduce the GPS / WAAS system. To do this, we first defined this system while passing by a brief presentation of GPS, presented its services and its architecture. In a second step, its operation was highlighted. In the continuation of our works, we intend to study this system in depth by focusing on the aspect of Precise Punctual Positioning (PPP). INTRODUCTION HISTORICAL ARCHITECTURE OPERATION CONCLUSION AND PERSPECTIVES SERVICES AND APPLICATIONS

26 THANK YOU FOR YOUR KIND ATTENTION


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