PART0 » History » Version 16
Version 15 (COLIN, Tony, 03/09/2016 11:10 PM) → Version 16/43 (COLIN, Tony, 03/09/2016 11:10 PM)
h1. PART 1 : An introduction to Navigation.
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p((. Before anything else, it is necessary to tackle the origin of navigation and its applications, the creation of the current GNSS with a comparison of different systems and finally, describing the main principles of GPS.
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h2. 1 - History of Navigation.
_*Navigation* is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another.[1] The field of navigation includes four general categories: land navigation, marine navigation, aeronautic navigation, and space navigation._
p=. !33.jpg! !34.jpg! !35.jpg! !37.jpg! !36.jpg!
h3. a- Visual navigation.
Seamark and landmark references > Limited range, Limited accuracy, Low availability of marks, Stars only during night and clear sky.
h3. b- Navigation with classic instruments
Magnetic compass, Sextant > Measurement of the height of stars above the horizon providing longitude inaccurately > Use of ephemeris and time reference
Improvements by combining it with Harrison's clock (Chronometer) providing latitude and longitude with acceptable accuracy.
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h2. 2 - Global Navigation Satellite System (GNSS).
h3. a- History.
- *Sputnik* in 1957 : first satellite in the world, orbit estimated using the received signal frequency : Doppler effect.
- *TRANSIT* from 1958 operational in 1964 : first satellite navigation system for the US Navy.
- *GPS* program started at 1973 providing position anywhere at anytime.
h3. b- Current definition.
_*Global Navigation Satellite System (GNSS)* is a system of satellites that provide autonomous spatial positioning on Earth with global coverage.
It allows small electronic receivers to determine their location (longitude/latitude/altitude) to high precision (within a few meters) using time signals transmitted along a line of sight by radio from satellites.
Global coverage for each system is generally achieved by a satellite constellation of 20–30 medium Earth orbit (MEO) satellites spread between several orbital planes. The actual systems vary, but use orbital inclinations of >50° and orbital periods of roughly 12 hours._
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h2. 3 - Comparison of systems.
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h2. 4 - Our system : GPS details.
_http://www.gps.gov/systems/gps/space/
https://en.wikipedia.org/wiki/Global_Positioning_System_
h3. a- Space Segment.
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h3. b- Ground Control Segment.
Continuously > Track GPS satellites, estimate clock and orbit, keep GPS time, upload data that describes clock & orbit for each satellite
Infrequently > Command small maneuvers to maintain orbit, small clock corrections, major relocations to compensate any satellite failure
h3. c- Delivery of Navigation messages.
Clock & Ephemeris sent by GS to SS, Spread Spectrum ranging signals & navigation data sent by SS to US & GS.
h3. d- Signals.
p=. !2.png!
h3. e- Ranging.
Propagation time : Time of transmission - Time of reception
Distance between satellite and receiver \approx Propagation time x Speed of light
How it works : attachment:"29.pdf"
_In geometry, *trilateration* is the process of determining absolute or relative locations of points by measurement of distances, using the geometry ofcircles, spheres or triangles. :_
1 measurement : 1 sphere of radius D1 centered in Sat1
2 measurements : intersection of 2 spheres (D1, Sat1) (D2, Sat2) = Circle
3 measurements : intersection of 3 spheres (D1, Sat1) (D2, Sat3) (D2, Sat3) = 2 points (1 often aberrant)
p=. !20.png!
h3. f- GNSS Receivers.
p=. !21.png!
p=. !22.png!
h3. g- GNSS Measurements.
p=. !23.png!
p=. !25-2.png!
p=. !24.png!
p=. !25.png!
*References :*
*[1]* M. Sahmoudi, Introduction to satellite positioning & multi-sensor navigation, 2016
*[2]* K. Borre, D. M. Akos, N. Bertelsen, P. Rinder, S. H. Jensen, A software-defined GPS and GALILEO receiver
*[3]* https://en.wikipedia.org/wiki/Satellite_navigation
*[4]* https://en.wikipedia.org/wiki/Global_Positioning_System
*[5]* http://www.gps.gov/systems/gps/
{{toc}} {{>toc}}
---
p((. Before anything else, it is necessary to tackle the origin of navigation and its applications, the creation of the current GNSS with a comparison of different systems and finally, describing the main principles of GPS.
---
h2. 1 - History of Navigation.
_*Navigation* is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another.[1] The field of navigation includes four general categories: land navigation, marine navigation, aeronautic navigation, and space navigation._
p=. !33.jpg! !34.jpg! !35.jpg! !37.jpg! !36.jpg!
h3. a- Visual navigation.
Seamark and landmark references > Limited range, Limited accuracy, Low availability of marks, Stars only during night and clear sky.
h3. b- Navigation with classic instruments
Magnetic compass, Sextant > Measurement of the height of stars above the horizon providing longitude inaccurately > Use of ephemeris and time reference
Improvements by combining it with Harrison's clock (Chronometer) providing latitude and longitude with acceptable accuracy.
---
h2. 2 - Global Navigation Satellite System (GNSS).
h3. a- History.
- *Sputnik* in 1957 : first satellite in the world, orbit estimated using the received signal frequency : Doppler effect.
- *TRANSIT* from 1958 operational in 1964 : first satellite navigation system for the US Navy.
- *GPS* program started at 1973 providing position anywhere at anytime.
h3. b- Current definition.
_*Global Navigation Satellite System (GNSS)* is a system of satellites that provide autonomous spatial positioning on Earth with global coverage.
It allows small electronic receivers to determine their location (longitude/latitude/altitude) to high precision (within a few meters) using time signals transmitted along a line of sight by radio from satellites.
Global coverage for each system is generally achieved by a satellite constellation of 20–30 medium Earth orbit (MEO) satellites spread between several orbital planes. The actual systems vary, but use orbital inclinations of >50° and orbital periods of roughly 12 hours._
---
h2. 3 - Comparison of systems.
p=. !31-2.png!
p=. !30.png!
---
h2. 4 - Our system : GPS details.
_http://www.gps.gov/systems/gps/space/
https://en.wikipedia.org/wiki/Global_Positioning_System_
h3. a- Space Segment.
p=. !26.png!
p=. !28-2.gif!
h3. b- Ground Control Segment.
Continuously > Track GPS satellites, estimate clock and orbit, keep GPS time, upload data that describes clock & orbit for each satellite
Infrequently > Command small maneuvers to maintain orbit, small clock corrections, major relocations to compensate any satellite failure
h3. c- Delivery of Navigation messages.
Clock & Ephemeris sent by GS to SS, Spread Spectrum ranging signals & navigation data sent by SS to US & GS.
h3. d- Signals.
p=. !2.png!
h3. e- Ranging.
Propagation time : Time of transmission - Time of reception
Distance between satellite and receiver \approx Propagation time x Speed of light
How it works : attachment:"29.pdf"
_In geometry, *trilateration* is the process of determining absolute or relative locations of points by measurement of distances, using the geometry ofcircles, spheres or triangles. :_
1 measurement : 1 sphere of radius D1 centered in Sat1
2 measurements : intersection of 2 spheres (D1, Sat1) (D2, Sat2) = Circle
3 measurements : intersection of 3 spheres (D1, Sat1) (D2, Sat3) (D2, Sat3) = 2 points (1 often aberrant)
p=. !20.png!
h3. f- GNSS Receivers.
p=. !21.png!
p=. !22.png!
h3. g- GNSS Measurements.
p=. !23.png!
p=. !25-2.png!
p=. !24.png!
p=. !25.png!
*References :*
*[1]* M. Sahmoudi, Introduction to satellite positioning & multi-sensor navigation, 2016
*[2]* K. Borre, D. M. Akos, N. Bertelsen, P. Rinder, S. H. Jensen, A software-defined GPS and GALILEO receiver
*[3]* https://en.wikipedia.org/wiki/Satellite_navigation
*[4]* https://en.wikipedia.org/wiki/Global_Positioning_System
*[5]* http://www.gps.gov/systems/gps/