If you wish to contribute or participate in the discussions about articles you are invited to contact the Editor

Combination of GNSS Measurements

From Navipedia
Revision as of 11:35, 24 June 2011 by Carlos.Lopez (talk | contribs) (Created page with "{{Article Infobox2 |Category=Fundamentals |Title={{PAGENAME}} |Authors= J. Sanz Subirana, JM. Juan Zornoza and M. Hernandez-Pajares, University of Catalunia, Spain. |Level=Medium...")
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to navigation Jump to search


FundamentalsFundamentals
Title Combination of GNSS Measurements
Author(s) J. Sanz Subirana, JM. Juan Zornoza and M. Hernandez-Pajares, University of Catalunia, Spain.
Level Medium
Year of Publication 2011
Logo gAGE.png


Starting from the basic observables (described in GNSS basic observables} the following combinations can be defined (where [math]\displaystyle{ R_{_{Pi}} }[/math] and [math]\displaystyle{ \Phi_{_{Li}} }[/math], [math]\displaystyle{ i=1,2 }[/math], indicate measurements in the frequencies [math]\displaystyle{ f_1 }[/math] and [math]\displaystyle{ f_2 }[/math]):


  • Ionosphere-free combination: It removes the first order (up to 99.9\%) ionospheric effect, which depends on the inverse square of the frequency ([math]\displaystyle{ \alpha_i \propto \frac{1}{f_i^2} }[/math], see article Ionospheric Delay).


[math]\displaystyle{ \Phi_{_{LC}}=\frac{f_1^2\;\Phi_{_{L1}}-f_2^2\;\Phi_{_{L2}}}{f_1^2-f_2^2}~~~~~;~~~~~ R_{_{PC}}=\frac{f_1^2\;R_{_{P1}}-f_2^2\;R_{_{P2}}}{f_1^2-f_2^2} }[/math]


Satellite clocks are defined relative to [math]\displaystyle{ R_{_{PC}} }[/math] combination (see article Combining pairs of signals and clock definition).

  • Geometry-free combination: it cancels the geometric part of the measurement, leaving all the frequency-dependent effects (i.e., ionospheric refraction, instrumental delays, wind-up) besides multipath and measurement noise. It can be used to estimate the ionospheric electron content, to detect cycle-slips in the carrier phase, or also to estimate antenna rotations as well. Note the change of terms order in [math]\displaystyle{ \Phi_{_{LI}} }[/math] and [math]\displaystyle{ R_{_{PI}} }[/math].


[math]\displaystyle{ \Phi_{_{LI}}=\Phi_{_{L1}}-\Phi_{_{L2}}~~~~~;~~~~~ R_{_{PI}}=R_{_{P2}}-R_{_{P1}} }[/math]


  • Wide-laning combinations: These combinations are used to create a signal with a significantly wide wavelength. This longer wavelength is useful for cycle-slips detection and ambiguity fixing. Other feature of this combination is the change of the sign in the ionospheric term, which is exploited by the Melbourne-Wübbena combination to remove the ionospheric refraction.


[math]\displaystyle{ \Phi_{_{LW}}=\frac{f_1\;\Phi_{_{L1}}-f_2\;\Phi_{_{L2}}}{f_1-f_2}~~~~~;~~~~~ R_{_{PW}}=\frac{f_1\;R_{_{P1}}-f_2\;R_{_{P2}}}{f_1-f_2} }[/math]


  • Narrow-laning combinations: These combinations create signals with a narrow wavelength. The signal in this combination has a lower noise than each separated component. It is used to reduce the code noise in the Melbourne-Wübbena combination to estimate the wide-lane ambiguity.


[math]\displaystyle{ \Phi_{_{LN}}=\frac{f_1\;\Phi_{_{L1}}+f_2\;\Phi_{_{L2}}}{f_1+f_2}~~~~~;~~~~~ R_{_{PN}}=\frac{f_1\;R_{_{P1}}+f_2\;R_{_{P2}}}{f_1+f_2} }[/math]

\end{itemize}


For more information, please go to the article:


Notes