Multipath - Revision history

Carlos.Lopez at 11:34, 23 February 2012

2012-02-23T11:34:22Z

← Older revision		Revision as of 11:34, 23 February 2012
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	\|Level=Intermediate		\|Level=Intermediate
	\|YearOfPublication=2011		\|YearOfPublication=2011
	~~\|Logo=gAGE~~
	\|Title={{PAGENAME}}		\|Title={{PAGENAME}}
	}}		}}

Jaume.Sanz at 18:01, 23 January 2012

2012-01-23T18:01:30Z

← Older revision		Revision as of 18:01, 23 January 2012
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	\|Title={{PAGENAME}}		\|Title={{PAGENAME}}
	}}		}}
	The interference by multipath is generated when a signal arrives, by different ways, at the antenna (see figure 1). Its principal cause is the antenna closeness to the reflecting structures, and it is important when the signal comes from the satellite with low elevation. This error is different for different frequencies. It affects the phase measurements, as well as the code measurements. In the case of the code, it can reach a theoretical value of 1.5 times the wavelength ("chip"). This means, for instance, that the multipath in the GPS ~~C/A~~ code can reach up to 450 meters (see table 1) although upper values more than 15 meters are difficult to observe. Typically, it is less than 2 or 3 meters.		The interference by multipath is generated when a signal arrives, by different ways, at the antenna (see figure 1). Its principal cause is the antenna closeness to the reflecting structures, and it is important when the signal comes from the satellite with low elevation. This error is different for different frequencies. It affects the phase measurements, as well as the code measurements. In the case of the code, it can reach a theoretical value of 1.5 times the wavelength ("chip"). This means, for instance, that the multipath in the GPS C1 code can reach up to 450 meters (see table 1) although upper values more than 15 meters are difficult to observe. Typically, it is less than 2 or 3 meters.

	::[[File: Signal_Structure_Table.png \|thumb\|none\|480px\| '''''Table 1: GPS signal structure (source: G. Seeber p. 217)]]		::[[File: Signal_Structure_Table.png \|thumb\|none\|480px\| '''''Table 1: GPS signal structure (source: G. Seeber p. 217)]]

Jaume.Sanz at 12:20, 16 January 2012

2012-01-16T12:20:59Z

← Older revision		Revision as of 12:20, 16 January 2012
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	The geometrical nature of multipath is illustrated in Figure 2, right, where the code minus phase combination <math>R_{_{P1}}-\Phi_{_{L1}}</math> is plotted for a given satellite for three consecutive days. The measurements were collected with a static GPS receiver and, thence, the geometry of satellite-receiver rays repeat every sidereal day <ref group="footnotes">That is every 24 hours minus 236 seconds of GPS time.</ref>. Notice in this figure how the multipath signatures overlaps after aligning the plots to the first day (i.e., by shifting <math>236</math> and <math>2 \times 236</math> seconds, the second and third day plots, respectively) to account for the difference between the sidereal and the solar times. The global drift is due to the ionospheric refraction <math>2 \alpha I</math>. (see equation 1)		The geometrical nature of multipath is illustrated in Figure 2, right, where the code minus phase combination <math>R_{_{P1}}-\Phi_{_{L1}}</math> is plotted for a given satellite for three consecutive days. The measurements were collected with a static GPS receiver and, thence, the geometry of satellite-receiver rays repeat every sidereal day <ref group="footnotes">That is every 24 hours minus 236 seconds of GPS time.</ref>. Notice in this figure how the multipath signatures overlaps after aligning the plots to the first day (i.e., by shifting <math>236</math> and <math>2 \times 236</math> seconds, the second and third day plots, respectively) to account for the difference between the sidereal and the solar times. The global drift is due to the ionospheric refraction <math>2 \alpha I</math>, (see equation 1):

	::<math>		::<math>

Jaume.Sanz at 12:18, 16 January 2012

2012-01-16T12:18:02Z

← Older revision		Revision as of 12:18, 16 January 2012
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	The effect of code multipath for low elevation rays is depicted in Figure 2, left, where the geometry-free combination of codes (<math>R_{_{P2}}-R_{_{P1}}</math>) and carrier (<math>\Phi_{_{L1}}-\Phi_{_{L2}}</math>) measurements are plotted for a satellite-receiver track. The largest noise in the edges is due to the low elevation rays at the rising and setting of the satellite. Notice that the carrier phase multipath (lower than <math>1</math> centimetre) can not be seen due to the scale of the figure, with <math>2</math> ~~meters~~ tics.		The effect of code multipath for low elevation rays is depicted in Figure 2, left, where the geometry-free combination of codes (<math>R_{_{P2}}-R_{_{P1}}</math>) and carrier (<math>\Phi_{_{L1}}-\Phi_{_{L2}}</math>) measurements are plotted for a satellite-receiver track. The largest noise in the edges is due to the low elevation rays at the rising and setting of the satellite. Notice that the carrier phase multipath (lower than <math>1</math> centimetre) can not be seen due to the scale of the figure, with <math>2</math> meter tics.

Jaume.Sanz at 12:11, 16 January 2012

2012-01-16T12:11:21Z

← Older revision		Revision as of 12:11, 16 January 2012
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	{{Article Infobox2		{{Article Infobox2
	\|Category=Fundamentals		\|Category=Fundamentals
	~~\|Title={{PAGENAME}}~~		\|Authors=J. Sanz Subirana, J.M. Juan Zornoza and M. Hernández-Pajares, Technical University of Catalonia, Spain.
	\|Authors= J. Sanz Subirana, JM. Juan Zornoza and M. ~~Hernandez~~-Pajares, University of ~~Catalunia~~, Spain.
	\|Level=Intermediate		\|Level=Intermediate
	\|YearOfPublication=2011		\|YearOfPublication=2011
	\|Logo=gAGE		\|Logo=gAGE
			\|Title={{PAGENAME}}
	}}		}}

	The interference by multipath is generated when a signal arrives, by different ways, at the antenna (see figure 1). Its principal cause is the antenna closeness to the reflecting structures, and it is important when the signal comes from the satellite with low elevation. This error is different for different frequencies. It affects the phase measurements, as well as the code measurements. In the case of the code, it can reach a theoretical value of 1.5 times the wavelength ("chip"). This means, for instance, that the multipath in the GPS C/A code can reach up to 450 meters (see table 1) although upper values more than 15 meters are difficult to observe. Typically, it is less than 2 or 3 meters.		The interference by multipath is generated when a signal arrives, by different ways, at the antenna (see figure 1). Its principal cause is the antenna closeness to the reflecting structures, and it is important when the signal comes from the satellite with low elevation. This error is different for different frequencies. It affects the phase measurements, as well as the code measurements. In the case of the code, it can reach a theoretical value of 1.5 times the wavelength ("chip"). This means, for instance, that the multipath in the GPS C/A code can reach up to 450 meters (see table 1) although upper values more than 15 meters are difficult to observe. Typically, it is less than 2 or 3 meters.

Timo.Kouwenhoven: Text replace - "|Level=Medium" to "|Level=Intermediate"

2011-11-06T07:45:58Z

Text replace - "|Level=Medium" to "|Level=Intermediate"

← Older revision		Revision as of 07:45, 6 November 2011
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	\|Title={{PAGENAME}}		\|Title={{PAGENAME}}
	\|Authors= J. Sanz Subirana, JM. Juan Zornoza and M. Hernandez-Pajares, University of Catalunia, Spain.		\|Authors= J. Sanz Subirana, JM. Juan Zornoza and M. Hernandez-Pajares, University of Catalunia, Spain.
	\|Level=~~Medium~~		\|Level=Intermediate
	\|YearOfPublication=2011		\|YearOfPublication=2011
	\|Logo=gAGE		\|Logo=gAGE

Carlos.Lopez at 15:25, 8 August 2011

2011-08-08T15:25:16Z

← Older revision		Revision as of 15:25, 8 August 2011
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	[[Category:Fundamentals]]		[[Category:Fundamentals]]
			[[Category:GNSS Measurements and Data Preprocessing]]

Carlos.Lopez at 10:50, 5 August 2011

2011-08-05T10:50:22Z

← Older revision		Revision as of 10:50, 5 August 2011
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	The interference by multipath is generated when a signal arrives, by different ways, at the antenna (see figure 1). Its principal cause is the antenna closeness to the reflecting structures, and it is important when the signal comes from the satellite with low elevation. This error is different for different frequencies. It affects the phase measurements, as well as the code measurements. In the case of the code, it can reach a theoretical value of 1.5 times the wavelength ("chip"). This means, for instance, that the multipath in the GPS C/A code can reach up to 450 meters (see table 1) although upper values more than 15 meters are difficult to observe. Typically, it is less than 2 or 3 meters.		The interference by multipath is generated when a signal arrives, by different ways, at the antenna (see figure 1). Its principal cause is the antenna closeness to the reflecting structures, and it is important when the signal comes from the satellite with low elevation. This error is different for different frequencies. It affects the phase measurements, as well as the code measurements. In the case of the code, it can reach a theoretical value of 1.5 times the wavelength ("chip"). This means, for instance, that the multipath in the GPS C/A code can reach up to 450 meters (see table 1) although upper values more than 15 meters are difficult to observe. Typically, it is less than 2 or 3 meters.

	::[[File: Signal_Structure_Table.png \|none\|480px\| '''''Table 1: GPS signal structure (source: G. Seeber p. 217)]]		::[[File: Signal_Structure_Table.png \|thumb\|none\|480px\| '''''Table 1: GPS signal structure (source: G. Seeber p. 217)]]


	In the case of the phase, its theoretical maximum value is a quarter of the wavelength. This means about 5 centimetres for the GPS L1 or L2 signals, but it is typically less than 1 centimetre.		In the case of the phase, its theoretical maximum value is a quarter of the wavelength. This means about 5 centimetres for the GPS L1 or L2 signals, but it is typically less than 1 centimetre.

	::[[File: Multipath_Fig_1.png\|none\|480px\| '''''Figure 1: Difference of the optical path between the direct signal and the reflected signal.]]		::[[File: Multipath_Fig_1.png\|thumb\|none\|480px\| '''''Figure 1: Difference of the optical path between the direct signal and the reflected signal.]]


	The multipath error can be minimised improving the antenna quality, that is to say, making them to mitigate the signal coming from certain low elevation directions, and moving the antenna away from reflecting objects (when possible).		The multipath error can be minimised improving the antenna quality, that is to say, making them to mitigate the signal coming from certain low elevation directions, and moving the antenna away from reflecting objects (when possible).


	The effect of code multipath for low elevation rays is depicted in Figure 2, left, where the geometry-free combination of codes (<math>R_{_{P2}}-R_{_{P1}}</math>) and carrier (<math>\Phi_{_{L1}}-\Phi_{_{L2}}</math>) measurements are plotted for a satellite-receiver track. The largest noise in the edges is due to the low elevation rays at the rising and setting of the satellite. Notice that the carrier phase multipath (lower than <math>1</math> centimetre) can not be seen due to the scale of the figure, with <math>2</math> meters tics.		The effect of code multipath for low elevation rays is depicted in Figure 2, left, where the geometry-free combination of codes (<math>R_{_{P2}}-R_{_{P1}}</math>) and carrier (<math>\Phi_{_{L1}}-\Phi_{_{L2}}</math>) measurements are plotted for a satellite-receiver track. The largest noise in the edges is due to the low elevation rays at the rising and setting of the satellite. Notice that the carrier phase multipath (lower than <math>1</math> centimetre) can not be seen due to the scale of the figure, with <math>2</math> meters tics.


	The geometrical nature of multipath is illustrated in Figure 2, right, where the code minus phase combination <math>R_{_{P1}}-\Phi_{_{L1}}</math> is plotted for a given satellite for three consecutive days. The measurements were collected with a static GPS receiver and, thence, the geometry of satellite-receiver rays repeat every sidereal day <ref group="footnotes">That is every 24 hours minus 236 seconds of GPS time.</ref>. Notice in this figure how the multipath signatures overlaps after aligning the plots to the first day (i.e., by shifting <math>236</math> and <math>2 \times 236</math> seconds, the second and third day plots, respectively) to account for the difference between the sidereal and the solar times. The global drift is due to the ionospheric refraction <math>2 \alpha I</math>. (see equation 1)		The geometrical nature of multipath is illustrated in Figure 2, right, where the code minus phase combination <math>R_{_{P1}}-\Phi_{_{L1}}</math> is plotted for a given satellite for three consecutive days. The measurements were collected with a static GPS receiver and, thence, the geometry of satellite-receiver rays repeat every sidereal day <ref group="footnotes">That is every 24 hours minus 236 seconds of GPS time.</ref>. Notice in this figure how the multipath signatures overlaps after aligning the plots to the first day (i.e., by shifting <math>236</math> and <math>2 \times 236</math> seconds, the second and third day plots, respectively) to account for the difference between the sidereal and the solar times. The global drift is due to the ionospheric refraction <math>2 \alpha I</math>. (see equation 1)

	<math>		::<math>
	R_1- \Phi_1=2 \tilde{\alpha}_1 I +Bias+\mathcal{M}+\varepsilon		R_1- \Phi_1=2 \tilde{\alpha}_1 I +Bias+\mathcal{M}+\varepsilon \qquad \mbox{(1)}
	</math>		</math>

	link to equation \emph{eq:L1P1} in the article \emph{Single frequency measurements smoothing}} (data set collected on 28-30 September 1998, in Barcelona (Spain), with the single frequency Lassen-SK8, Trimble, receiver).

	::{\|		::{\|

Carlos.Lopez at 15:01, 19 July 2011

2011-07-19T15:01:29Z

@@ Line 1: / Line 1: @@
 The interference by multipath is generated when a signal arrives, by different ways, at the antenna (see figure 1). Its principal cause is the antenna closeness to the reflecting structures, and it is important when the signal comes from the satellite with low elevation. This error is different for different frequencies. It affects the phase measurements, as well as the code measurements. In the case of the code, it can reach a theoretical value of 1.5 times the wavelength ("chip"). This means, for instance, that the multipath in the GPS C/A code can reach up to 450 meters (see table 1) although upper values more than 15 meters are difficult to observe. Typically, it is less than 2 or 3 meters.
@@ Line 12: / Line 20: @@
 The effect of code multipath for low elevation rays is depicted in Figure 2, left, where the geometry-free combination of codes  (<math>R_{_{P2}}-R_{_{P1}}</math>)  and carrier  (<math>\Phi_{_{L1}}-\Phi_{_{L2}}</math>) measurements are plotted for a satellite-receiver track. The largest noise in the edges is due to the low elevation rays at the rising and setting of the satellite. Notice that the carrier phase multipath (lower than <math>1</math> centimetre) can not be seen due to the scale of the figure, with <math>2</math> meters tics.
 The geometrical nature of multipath is illustrated in Figure 2, right, where the code minus phase combination <math>R_{_{P1}}-\Phi_{_{L1}}</math> is plotted for a given satellite for three consecutive days. The measurements were collected with a static GPS receiver and, thence, the geometry of satellite-receiver rays repeat every sidereal day <ref group="footnotes">That is every 24 hours minus 236 seconds of GPS time.</ref>. Notice in this figure how the multipath signatures overlaps after aligning the plots to the first day (i.e., by shifting <math>236</math> and <math>2 \times 236</math> seconds, the second and third day plots, respectively) to account for the difference between the sidereal and the solar times. The global drift is due to the ionospheric refraction <math>2 \alpha I</math>. (see equation 1)

Carlos.Lopez: Created page with " The interference by multipath is generated when a signal arrives, by different ways, at the antenna (see figure 1). Its principal cause is the antenna closeness to the reflectin..."

2011-07-19T15:01:03Z

Created page with " The interference by multipath is generated when a signal arrives, by different ways, at the antenna (see figure 1). Its principal cause is the antenna closeness to the reflectin..."

New page

The interference by multipath is generated when a signal arrives, by different ways, at the antenna (see figure 1). Its principal cause is the antenna closeness to the reflecting structures, and it is important when the signal comes from the satellite with low elevation. This error is different for different frequencies. It affects the phase measurements, as well as the code measurements. In the case of the code, it can reach a theoretical value of 1.5 times the wavelength ("chip"). This means, for instance, that the multipath in the GPS C/A code can reach up to 450 meters (see table 1) although upper values more than 15 meters are difficult to observe. Typically, it is less than 2 or 3 meters.

::[[File: Signal_Structure_Table.png |none|480px| '''''Table 1: GPS signal structure (source: G. Seeber p. 217)]]

In the case of the phase, its theoretical maximum value is a quarter of the wavelength. This means about 5 centimetres for the GPS L1 or L2 signals, but it is typically less than 1 centimetre.

::[[File: Multipath_Fig_1.png|none|480px| '''''Figure 1: Difference of the optical path between the direct signal and the reflected signal.]]

The multipath error can be minimised improving the antenna quality, that is to say, making them to mitigate the signal coming from certain low elevation directions, and moving the antenna away from reflecting objects (when possible).

The effect of code multipath for low elevation rays is depicted in Figure 2, left, where the geometry-free combination of codes (<math>R_{_{P2}}-R_{_{P1}}</math>) and carrier (<math>\Phi_{_{L1}}-\Phi_{_{L2}}</math>) measurements are plotted for a satellite-receiver track. The largest noise in the edges is due to the low elevation rays at the rising and setting of the satellite. Notice that the carrier phase multipath (lower than <math>1</math> centimetre) can not be seen due to the scale of the figure, with <math>2</math> meters tics.
{{Article Infobox2
|Category=Fundamentals
|Title={{PAGENAME}}
|Authors= J. Sanz Subirana, JM. Juan Zornoza and M. Hernandez-Pajares, University of Catalunia, Spain.
|Level=Medium
|YearOfPublication=2011
|Logo=gAGE
}}

The geometrical nature of multipath is illustrated in Figure 2, right, where the code minus phase combination <math>R_{_{P1}}-\Phi_{_{L1}}</math> is plotted for a given satellite for three consecutive days. The measurements were collected with a static GPS receiver and, thence, the geometry of satellite-receiver rays repeat every sidereal day <ref group="footnotes">That is every 24 hours minus 236 seconds of GPS time.</ref>. Notice in this figure how the multipath signatures overlaps after aligning the plots to the first day (i.e., by shifting <math>236</math> and <math>2 \times 236</math> seconds, the second and third day plots, respectively) to account for the difference between the sidereal and the solar times. The global drift is due to the ionospheric refraction <math>2 \alpha I</math>. (see equation 1)

<math>
R_1- \Phi_1=2 \tilde{\alpha}_1 I +Bias+\mathcal{M}+\varepsilon
</math>

link to equation \emph{eq:L1P1} in the article \emph{Single frequency measurements smoothing}} (data set collected on 28-30 September 1998, in Barcelona (Spain), with the single frequency Lassen-SK8, Trimble, receiver).

::{|
|+align="bottom"|''Figure 2: Satellite Effect of code multipath on GPS signals. Figure at left shows the "butterfly effect" due to the largest multipath at the satellite rising and setting (i.e., due to the low elevation rays). The figure at right shows the repeatability of multipath signatures with the geometry: The code minus phase signal combination <math>R_{_{P1}}-\Phi_{_{L1}}</math> is plotted for a given satellite for three consecutive sidereal days. The drift is due to the ionospheric refraction. Note: Data set collected on 28-30 September 1998, in Barcelona (Spain), with the single frequency Lassen-SK8, Trimble, receiver)''

| [[File: Multipath_Fig_2.png|none|thumb|400px|frameless]]
| [[File: Multipath_Fig_3.png|none|thumb|400px|frameless]]
|}

==Notes==
<references group="footnotes"/>

[[Category:Fundamentals]]