GPS General Introduction - Revision history

Gema.Cueto: /* GPS Future and Evolutions */

2021-01-29T11:28:03Z

GPS Future and Evolutions

← Older revision		Revision as of 11:28, 29 January 2021
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	* L2C (1227.6 MHz: It enables the development of dual-frequency civil GPS receivers to correct the ionospheric group delay. This signal is available since 2005, with the launch of the first IIR-M satellite.<ref>[https://web.stanford.edu/group/scpnt/pnt/PNT10/presentation_slides/2-PNT_Symposium_Gruber.pdf GPS Modernization and Program Update, Bernie Gruber]</ref>		* L2C (1227.6 MHz: It enables the development of dual-frequency civil GPS receivers to correct the ionospheric group delay. This signal is available since 2005, with the launch of the first IIR-M satellite.<ref>[https://web.stanford.edu/group/scpnt/pnt/PNT10/presentation_slides/2-PNT_Symposium_Gruber.pdf GPS Modernization and Program Update, Bernie Gruber]</ref>
	* L5C (1176.45 MHz): It is compatible with other GNSS systems and is transmitted at a higher power than current civil GPS signals, also with a wider bandwidth. This signal is available since the launch of the Block IIF satellites (May 28th 2010).		* L5C (1176.45 MHz): It is compatible with other GNSS systems and is transmitted at a higher power than current civil GPS signals, also with a wider bandwidth. This signal is available since the launch of the Block IIF satellites (May 28th 2010).
	* L1C (1575.42 MHz): Designed for interoperability with Galileo, it is backward compatible with the current civil signal on L1. This signal is available since the launch of the Block IIIA satellites (first satellite launched December 2018). An enhancement to this L1C signal is being analysed, which is called CHIMERA (Chips Message Robust Authentication). This technique consists on adding encrypted watermarks to the L1C signal that not only let users know when a signal is being spoofed but also makes it possible to authenticate the location of a GPS receiver to another party.		* L1C (1575.42 MHz): Designed for interoperability with Galileo, it is backward compatible with the current civil signal on L1. This signal is available since the launch of the Block IIIA satellites (first satellite launched December 2018). An enhancement to this L1C signal is being analysed, which is called CHIMERA (Chips Message Robust Authentication). This technique consists on adding encrypted watermarks to the L1C signal that not only let users know when a signal is being spoofed but also makes it possible to [[GNSS Authentication and encryption \| authenticate]] the location of a GPS receiver to another party.

	In addition to the civil signals, it is planned to include a new military signal, the M-code, in L1 and L2 frequencies.<ref>[http://www.navcen.uscg.gov/pdf/ModernizedL2CivilSignal.pdf The Modernized L2 Civil Signal, by Richard D. Fontana, Wai Cheung, and Tom Stansell, GPS World September 2001]</ref>		In addition to the civil signals, it is planned to include a new military signal, the M-code, in L1 and L2 frequencies.<ref>[http://www.navcen.uscg.gov/pdf/ModernizedL2CivilSignal.pdf The Modernized L2 Civil Signal, by Richard D. Fontana, Wai Cheung, and Tom Stansell, GPS World September 2001]</ref>

Gema.Cueto: /* GPS Services */

2020-12-15T12:27:59Z

GPS Services

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	GPS provides two different positioning [[GPS Services\|services]], namely the Precise Positioning Service (PPS) and the Standard Positioning Service (SPS):		GPS provides two different positioning [[GPS Services\|services]], namely the Precise Positioning Service (PPS) and the Standard Positioning Service (SPS):
	# The Standard Positioning Service (SPS),<ref name="SPS-Standard ">[https://www.gps.gov/technical/ps/2020-SPS-performance-standard.pdf Global Positioning System Standard Positioning Service Performance Standard]</ref> is a positioning and timing service provided on GPS L1, L2 and L5 frequencies and available to all GPS users. The L1 frequency contains a coarse acquisition (C/A) code and a navigation data message. The L2 frequency contains a CM-code and CL-code signals whereas I5-code and Q5-code signals are transmitted in L5 frequency.		# The Standard Positioning Service (SPS),<ref name="SPS-Standard ">[https://www.gps.gov/technical/ps/2020-SPS-performance-standard.pdf Global Positioning System Standard Positioning Service Performance Standard]</ref> is a positioning and timing service provided on GPS L1, L2 and L5 frequencies and available to all GPS users. The L1 frequency contains a coarse acquisition (C/A) code and a navigation data message. The L2 frequency contains a CM-code and CL-code signals whereas I5-code and Q5-code signals are transmitted in L5 frequency.
	# The Precise Positioning Service (PPS),<ref name ="~~PSP~~">[~~https~~://www.gps.gov/technical/ps/2007-PPS-performance-standard.pdf Global Positioning System Precise Positioning Service Performance Standard]</ref> is a highly accurate military positioning, velocity and timing service broadcasted at the GPS L1 and L2 frequencies. Both frequencies contain a precision (P) code ranging signal with a navigation data message that is reserved for authorized use by the use of cryptography.		# The Precise Positioning Service (PPS.<ref name="PPS-Standard">[http://www.gps.gov/technical/ps/2007-PPS-performance-standard.pdf Global Positioning System Precise Positioning Service Performance Standard]</ref> is a highly accurate military positioning, velocity and timing service broadcasted at the GPS L1 and L2 frequencies. Both frequencies contain a precision (P) code ranging signal with a navigation data message that is reserved for authorized use by the use of cryptography.

	==GPS Architecture==		==GPS Architecture==

Gema.Cueto: /* GPS Services */

2020-12-15T12:27:14Z

GPS Services

← Older revision		Revision as of 12:27, 15 December 2020
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	GPS provides two different positioning [[GPS Services\|services]], namely the Precise Positioning Service (PPS) and the Standard Positioning Service (SPS):		GPS provides two different positioning [[GPS Services\|services]], namely the Precise Positioning Service (PPS) and the Standard Positioning Service (SPS):
	# The Standard Positioning Service (SPS),<ref name="SPS-Standard ">[https://www.gps.gov/technical/ps/2020-SPS-performance-standard.pdf Global Positioning System Standard Positioning Service Performance Standard]</ref> is a positioning and timing service provided on GPS L1, L2 and L5 frequencies and available to all GPS users. The L1 frequency contains a coarse acquisition (C/A) code and a navigation data message. The L2 frequency contains a CM-code and CL-code signals whereas I5-code and Q5-code signals are transmitted in L5 frequency.		# The Standard Positioning Service (SPS),<ref name="SPS-Standard ">[https://www.gps.gov/technical/ps/2020-SPS-performance-standard.pdf Global Positioning System Standard Positioning Service Performance Standard]</ref> is a positioning and timing service provided on GPS L1, L2 and L5 frequencies and available to all GPS users. The L1 frequency contains a coarse acquisition (C/A) code and a navigation data message. The L2 frequency contains a CM-code and CL-code signals whereas I5-code and Q5-code signals are transmitted in L5 frequency.

	# The Precise Positioning Service (PPS),<ref name ="PSP">[https://www.gps.gov/technical/ps/2007-PPS-performance-standard.pdf Global Positioning System Precise Positioning Service Performance Standard]</ref> is a highly accurate military positioning, velocity and timing service broadcasted at the GPS L1 and L2 frequencies. Both frequencies contain a precision (P) code ranging signal with a navigation data message that is reserved for authorized use by the use of cryptography.		# The Precise Positioning Service (PPS),<ref name ="PSP">[https://www.gps.gov/technical/ps/2007-PPS-performance-standard.pdf Global Positioning System Precise Positioning Service Performance Standard]</ref> is a highly accurate military positioning, velocity and timing service broadcasted at the GPS L1 and L2 frequencies. Both frequencies contain a precision (P) code ranging signal with a navigation data message that is reserved for authorized use by the use of cryptography.

Gema.Cueto: /* GPS Services */

2020-12-15T12:26:58Z

GPS Services

← Older revision		Revision as of 12:26, 15 December 2020
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	GPS provides two different positioning [[GPS Services\|services]], namely the Precise Positioning Service (PPS) and the Standard Positioning Service (SPS):		GPS provides two different positioning [[GPS Services\|services]], namely the Precise Positioning Service (PPS) and the Standard Positioning Service (SPS):
	# The Standard Positioning Service (SPS),<ref name="SPS-Standard ">[https://www.gps.gov/technical/ps/2020-SPS-performance-standard.pdf Global Positioning System Standard Positioning Service Performance Standard]</ref> is a positioning and timing service provided on GPS L1, L2 and L5 frequencies and available to all GPS users. The L1 frequency contains a coarse acquisition (C/A) code and a navigation data message. The L2 frequency contains a CM-code and CL-code signals whereas I5-code and Q5-code signals are transmitted in L5 frequency.		# The Standard Positioning Service (SPS),<ref name="SPS-Standard ">[https://www.gps.gov/technical/ps/2020-SPS-performance-standard.pdf Global Positioning System Standard Positioning Service Performance Standard]</ref> is a positioning and timing service provided on GPS L1, L2 and L5 frequencies and available to all GPS users. The L1 frequency contains a coarse acquisition (C/A) code and a navigation data message. The L2 frequency contains a CM-code and CL-code signals whereas I5-code and Q5-code signals are transmitted in L5 frequency.

			# The Precise Positioning Service (PPS),<ref name ="PSP">[https://www.gps.gov/technical/ps/2007-PPS-performance-standard.pdf Global Positioning System Precise Positioning Service Performance Standard]</ref> is a highly accurate military positioning, velocity and timing service broadcasted at the GPS L1 and L2 frequencies. Both frequencies contain a precision (P) code ranging signal with a navigation data message that is reserved for authorized use by the use of cryptography.

	==GPS Architecture==		==GPS Architecture==

Gema.Cueto: /* GPS Services */

2020-12-15T12:16:52Z

GPS Services

← Older revision		Revision as of 12:16, 15 December 2020
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	==GPS Services==		==GPS Services==
	GPS provides two different positioning [[GPS Services\|services]], namely the Precise Positioning Service (PPS) and the Standard Positioning Service (SPS):		GPS provides two different positioning [[GPS Services\|services]], namely the Precise Positioning Service (PPS) and the Standard Positioning Service (SPS):
	# The Standard Positioning Service (SPS),<ref name="SPS-Standard ">[https://www.gps.gov/technical/ps/2020-SPS-performance-standard.pdf Global Positioning System Standard Positioning Service Performance Standard]</ref> is a positioning and timing service provided on GPS L1 ~~frequency~~ and available to all GPS users. The L1~~, L2 and L5 frequencies~~ contains a coarse acquisition (C/A) code and a navigation data message. The L2 frequency contains a CM-code and CL-code signals whereas I5-code and Q5-code signals are transmitted in L5 frequency.		# The Standard Positioning Service (SPS),<ref name="SPS-Standard ">[https://www.gps.gov/technical/ps/2020-SPS-performance-standard.pdf Global Positioning System Standard Positioning Service Performance Standard]</ref> is a positioning and timing service provided on GPS L1, L2 and L5 frequencies and available to all GPS users. The L1 frequency contains a coarse acquisition (C/A) code and a navigation data message. The L2 frequency contains a CM-code and CL-code signals whereas I5-code and Q5-code signals are transmitted in L5 frequency.
	# The Precise Positioning Service (PPS),<ref name="PPS-Standard "/> is a highly accurate military positioning, velocity and timing service broadcasted at the GPS L1 and L2 frequencies. Both frequencies contain a precision (P) code ranging signal with a navigation data message that is reserved for authorized use by the use of cryptography.

	==GPS Architecture==		==GPS Architecture==

Gema.Cueto: /* GPS Services */

2020-12-14T07:50:06Z

GPS Services

← Older revision		Revision as of 07:50, 14 December 2020
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	==GPS Services==		==GPS Services==
	GPS provides two different positioning [[GPS Services\|services]], namely the Precise Positioning Service (PPS) and the Standard Positioning Service (SPS):		GPS provides two different positioning [[GPS Services\|services]], namely the Precise Positioning Service (PPS) and the Standard Positioning Service (SPS):
	# The Standard Positioning Service (SPS),<ref name="SPS-Standard ">[~~http~~://www.gps.gov/technical/ps/~~2008~~-SPS-performance-standard.pdf Global Positioning System Standard Positioning Service Performance Standard]</ref> is a positioning and timing service provided on GPS L1 frequency and available to all GPS users. The L1, L2 and L5 frequencies contains a coarse acquisition (C/A) code and a navigation data message. The L2 frequency contains a CM-code and CL-code signals whereas I5-code and Q5-code signals are transmitted in L5 frequency.		# The Standard Positioning Service (SPS),<ref name="SPS-Standard ">[https://www.gps.gov/technical/ps/2020-SPS-performance-standard.pdf Global Positioning System Standard Positioning Service Performance Standard]</ref> is a positioning and timing service provided on GPS L1 frequency and available to all GPS users. The L1, L2 and L5 frequencies contains a coarse acquisition (C/A) code and a navigation data message. The L2 frequency contains a CM-code and CL-code signals whereas I5-code and Q5-code signals are transmitted in L5 frequency.
	# The Precise Positioning Service (PPS),<ref name="PPS-Standard "/> is a highly accurate military positioning, velocity and timing service broadcasted at the GPS L1 and L2 frequencies. Both frequencies contain a precision (P) code ranging signal with a navigation data message that is reserved for authorized use by the use of cryptography.		# The Precise Positioning Service (PPS),<ref name="PPS-Standard "/> is a highly accurate military positioning, velocity and timing service broadcasted at the GPS L1 and L2 frequencies. Both frequencies contain a precision (P) code ranging signal with a navigation data message that is reserved for authorized use by the use of cryptography.

Gema.Cueto at 07:47, 14 December 2020

2020-12-14T07:47:12Z

← Older revision		Revision as of 07:47, 14 December 2020
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	Originally developed for the U.S. military, the incident with the Korean Air Lines Flight 007<ref>[http://en.wikipedia.org/wiki/Korean_Air_Lines_Flight_007 Korean Air Lines Flight 007]</ref> led the US Government to decide to make GPS use free for civilian purposes very early in the experimental phase of GPS .<ref>[http://en.wikipedia.org/wiki/Global_Positioning_System Global Positioning System on Wikipedia]</ref>		Originally developed for the U.S. military, the incident with the Korean Air Lines Flight 007<ref>[http://en.wikipedia.org/wiki/Korean_Air_Lines_Flight_007 Korean Air Lines Flight 007]</ref> led the US Government to decide to make GPS use free for civilian purposes very early in the experimental phase of GPS .<ref>[http://en.wikipedia.org/wiki/Global_Positioning_System Global Positioning System on Wikipedia]</ref>
	The launch of the first Block I Navstar GPS satellite meant the beginning of the deployment of the GPS system on 22 February 1978,<ref>[http://www.astronautix.com/g/gpsblock1.html Block 1 Satellite Information]</ref> followed by the declaration of the Initial Operating Capability in December 1993 with 24 operational satellites in orbit, and the Full Operational Capability in June 1995.		The launch of the first Block I Navstar GPS satellite meant the beginning of the deployment of the GPS system on 22 February 1978,<ref>[http://www.astronautix.com/g/gpsblock1.html Block 1 Satellite Information]</ref> followed by the declaration of the Initial Operating Capability in December 1993 with 24 operational satellites in orbit, and the Full Operational Capability in June 1995.
	GPS is maintained by the United States government and is freely accessible by anyone with a GPS receiver. The Department of Defense is responsible for operating the system, but it also receives national-level attention and guidance through the National Executive Committee for Space-Based Positioning, Navigation, and Timing (PNT).<ref>[~~http~~://www.gps.gov/~~policy~~/~~agencies~~ Federal Agencies]</ref>		GPS is maintained by the United States government and is freely accessible by anyone with a GPS receiver. The Department of Defense is responsible for operating the system, but it also receives national-level attention and guidance through the National Executive Committee for Space-Based Positioning, Navigation, and Timing (PNT).<ref>[https://www.gps.gov/governance/excom/ Federal Agencies]</ref>

	[[File:GPS_satellite_block_IIR_M.png\|GPS block IIR-M satellite\|thumb\|right\|300px]]		[[File:GPS_satellite_block_IIR_M.png\|GPS block IIR-M satellite\|thumb\|right\|300px]]

Gema.Cueto: /* GPS Future and Evolutions */

2020-12-14T07:43:54Z

GPS Future and Evolutions

← Older revision		Revision as of 07:43, 14 December 2020
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	Aimed at improving the performance for civilian users, the [[GPS Future and Evolutions\|GPS modernization]] will introduce the following signals:<ref>[http://www.gps.gov/systems/gps/modernization/2006-fact-sheet.pdf GPS Modernization Fact Sheet]</ref><ref>[https://www.gps.gov/systems/gps/modernization/ GPS Official website]</ref>		Aimed at improving the performance for civilian users, the [[GPS Future and Evolutions\|GPS modernization]] will introduce the following signals:<ref>[http://www.gps.gov/systems/gps/modernization/2006-fact-sheet.pdf GPS Modernization Fact Sheet]</ref><ref>[https://www.gps.gov/systems/gps/modernization/ GPS Official website]</ref>
	* L2C (1227.6 MHz: It enables the development of dual-frequency civil GPS receivers to correct the ionospheric group delay. This signal is available since 2005, with the launch of the first IIR-M satellite.<ref>[https://web.stanford.edu/group/scpnt/pnt/PNT10/presentation_slides/2-PNT_Symposium_Gruber.pdf GPS Modernization and Program Update, Bernie Gruber]</ref>		* L2C (1227.6 MHz: It enables the development of dual-frequency civil GPS receivers to correct the ionospheric group delay. This signal is available since 2005, with the launch of the first IIR-M satellite.<ref>[https://web.stanford.edu/group/scpnt/pnt/PNT10/presentation_slides/2-PNT_Symposium_Gruber.pdf GPS Modernization and Program Update, Bernie Gruber]</ref>
	* L5C (1176.45 MHz): It ~~will be~~ compatible with other GNSS systems and ~~will transmit~~ at a higher power than current civil GPS signals, ~~and have~~ a wider bandwidth. This signal is available since the launch of the Block IIF satellites (May 28th 2010).		* L5C (1176.45 MHz): It is compatible with other GNSS systems and is transmitted at a higher power than current civil GPS signals, also with a wider bandwidth. This signal is available since the launch of the Block IIF satellites (May 28th 2010).
	* L1C (1575.42 MHz): Designed for interoperability with Galileo, it ~~will be~~ backward compatible with the current civil signal on L1. This signal ~~will be broadcast from~~ Block IIIA satellites		* L1C (1575.42 MHz): Designed for interoperability with Galileo, it is backward compatible with the current civil signal on L1. This signal is available since the launch of the Block IIIA satellites (first satellite launched December 2018). An enhancement to this L1C signal is being analysed, which is called CHIMERA (Chips Message Robust Authentication). This technique consists on adding encrypted watermarks to the L1C signal that not only let users know when a signal is being spoofed but also makes it possible to authenticate the location of a GPS receiver to another party.

	In addition to the civil signals, it is planned to include a new military signal, the M-code, in L1 and L2 frequencies.<ref>[http://www.navcen.uscg.gov/pdf/ModernizedL2CivilSignal.pdf The Modernized L2 Civil Signal, by Richard D. Fontana, Wai Cheung, and Tom Stansell, GPS World September 2001]</ref>		In addition to the civil signals, it is planned to include a new military signal, the M-code, in L1 and L2 frequencies.<ref>[http://www.navcen.uscg.gov/pdf/ModernizedL2CivilSignal.pdf The Modernized L2 Civil Signal, by Richard D. Fontana, Wai Cheung, and Tom Stansell, GPS World September 2001]</ref>

Gema.Cueto: /* GPS Future and Evolutions */

2020-12-14T07:40:46Z

GPS Future and Evolutions

← Older revision		Revision as of 07:40, 14 December 2020
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	==GPS Future and Evolutions==		==GPS Future and Evolutions==
	Aimed at improving the performance for civilian users, the [[GPS Future and Evolutions\|GPS modernization]] will introduce the following signals:<ref>[http://www.gps.gov/systems/gps/modernization/2006-fact-sheet.pdf GPS Modernization Fact Sheet]</ref>		Aimed at improving the performance for civilian users, the [[GPS Future and Evolutions\|GPS modernization]] will introduce the following signals:<ref>[http://www.gps.gov/systems/gps/modernization/2006-fact-sheet.pdf GPS Modernization Fact Sheet]</ref><ref>[https://www.gps.gov/systems/gps/modernization/ GPS Official website]</ref>
	* L2C (1227.6 MHz: It enables the development of dual-frequency civil GPS receivers to correct the ionospheric group delay. This signal is available since 2005, with the launch of the first IIR-M satellite.<ref>[https://web.stanford.edu/group/scpnt/pnt/PNT10/presentation_slides/2-PNT_Symposium_Gruber.pdf GPS Modernization and Program Update, Bernie Gruber]</ref>		* L2C (1227.6 MHz: It enables the development of dual-frequency civil GPS receivers to correct the ionospheric group delay. This signal is available since 2005, with the launch of the first IIR-M satellite.<ref>[https://web.stanford.edu/group/scpnt/pnt/PNT10/presentation_slides/2-PNT_Symposium_Gruber.pdf GPS Modernization and Program Update, Bernie Gruber]</ref>
	* L5C (1176.45 MHz): It will be compatible with other GNSS systems and will transmit at a higher power than current civil GPS signals, and have a wider bandwidth. This signal is available since the launch of the Block IIF satellites (May 28th 2010).		* L5C (1176.45 MHz): It will be compatible with other GNSS systems and will transmit at a higher power than current civil GPS signals, and have a wider bandwidth. This signal is available since the launch of the Block IIF satellites (May 28th 2010).

Gema.Cueto: /* GPS Architecture */

2020-12-14T07:34:02Z

GPS Architecture

← Older revision		Revision as of 07:34, 14 December 2020
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	[[GPS Architecture\|GPS architecture]] is comprised of three segments: a [[GPS Space Segment\|GPS Space Segment]], a [[GPS Ground Segment\|GPS Ground Segment]], and a [[GPS User Segment\|GPS User Segment]].		[[GPS Architecture\|GPS architecture]] is comprised of three segments: a [[GPS Space Segment\|GPS Space Segment]], a [[GPS Ground Segment\|GPS Ground Segment]], and a [[GPS User Segment\|GPS User Segment]].
	The main functions of the [[GPS Space Segment\|GPS Space Segment]] are to transmit radio-navigation signals, and to store and retransmit the navigation message sent by the [[GPS Ground Segment\|GPS Ground Segment]].		The main functions of the [[GPS Space Segment\|GPS Space Segment]] are to transmit radio-navigation signals, and to store and retransmit the navigation message sent by the [[GPS Ground Segment\|GPS Ground Segment]].
	The [[GPS Ground Segment\|GPS Ground Segment]] is composed of a master control station, a network of monitor stations and ~~four~~ ground antennas which upload the clock and orbit errors, as well as the navigation data message to the GPS satellites.<ref name="GNSS-Book "/>		The [[GPS Ground Segment\|GPS Ground Segment]] is composed of a master control station, a network of monitor stations and ground antennas which upload the clock and orbit errors, as well as the navigation data message to the GPS satellites.<ref name="GNSS-Book "/>
	Finally, the [[GPS User Segment\|GPS User Segment]] consists on the millions of receivers performing the navigation, timing or other related functions.		Finally, the [[GPS User Segment\|GPS User Segment]] consists on the millions of receivers performing the navigation, timing or other related functions.

	==Differential GPS==		==Differential GPS==

← Older revision		Revision as of 07:34, 14 December 2020
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	[[GPS Architecture\|GPS architecture]] is comprised of three segments: a [[GPS Space Segment\|GPS Space Segment]], a [[GPS Ground Segment\|GPS Ground Segment]], and a [[GPS User Segment\|GPS User Segment]].		[[GPS Architecture\|GPS architecture]] is comprised of three segments: a [[GPS Space Segment\|GPS Space Segment]], a [[GPS Ground Segment\|GPS Ground Segment]], and a [[GPS User Segment\|GPS User Segment]].
	The main functions of the [[GPS Space Segment\|GPS Space Segment]] are to transmit radio-navigation signals, and to store and retransmit the navigation message sent by the [[GPS Ground Segment\|GPS Ground Segment]].		The main functions of the [[GPS Space Segment\|GPS Space Segment]] are to transmit radio-navigation signals, and to store and retransmit the navigation message sent by the [[GPS Ground Segment\|GPS Ground Segment]].
	The [[GPS Ground Segment\|GPS Ground Segment]] is composed of a master control station, a network of monitor stations and ~~four~~ ground antennas which upload the clock and orbit errors, as well as the navigation data message to the GPS satellites.<ref name="GNSS-Book "/>		The [[GPS Ground Segment\|GPS Ground Segment]] is composed of a master control station, a network of monitor stations and ground antennas which upload the clock and orbit errors, as well as the navigation data message to the GPS satellites.<ref name="GNSS-Book "/>
	Finally, the [[GPS User Segment\|GPS User Segment]] consists on the millions of receivers performing the navigation, timing or other related functions.		Finally, the [[GPS User Segment\|GPS User Segment]] consists on the millions of receivers performing the navigation, timing or other related functions.

	==Differential GPS==		==Differential GPS==