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|Category=Fundamentals
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|Title={{PAGENAME}}
|Editors=GMV
|Authors=GMV
|Level=Basic
|Level=Basic
|YearOfPublication=2011
|YearOfPublication=2011
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In [[Real Time Kinematics|Real Time Kinematics (RTK)]], the compensation of the ionospheric delay between the base station and each of the roving users works for baselines up to 10-20 kilometers. When using a network of base stations, [[RTK Systems|Network RTK]] (NRTK), to mitigate atmospheric dependent effects over distance, the allowed distance between baselines and rovers increases up to 50-70 kms. In the late 1990s, the '''Wide Area RTK''' concept was introduced by the [http://www.gage.es/ Research Group of Astronomy and Geomatics (gAGE)] from the Technical University of Catalonia (UPC) to address these problems.


In [[Real Time Kinematics (RTK)]], the assumption that the differential ionospheric delay between a GNSS transmitter and each of the roving or reference receivers is negligible works well for baselines up to 10-20 kilometers. A refinement of this assumption comes with the network RTK (NRTK) using a set of permanent receivers to mitigate atmospheric dependent effects over distance, increasing the allowed distance between baselines and rovers up to 50-70 kms. The '''Wide Area RTK''' concept was introduced in thelate 1990s to address these deficiencies by the [http://www.gage.es/ Research Group of Astronomy and Geomatics (gAGE)] from the Technical University of Catalonia (UPC).
==Wide-Area Real-Time Kinematics (WARTK)==


==Differential GNSS==
Starting in late 90's until nowadays, the group [http://www.gage.es/ gAGE/UPC] has developed the Wide-Area Real-Time Kinematics (WARTK) technique, which allows the extension of local services based on the real-time carrier phase ambiguity resolution to wide-area scale (i.e. baselines between the rover and reference stations greater than 100 km), for both dual-frequency (only GPS) and 3-frequency systems (also with Galileo and modernized GPS). The Wide-Area Real-Time Kinematics (WARTK) technique for dual and 3-frequency systems are based on an optimal combination of accurate ionospheric and geodetic models in a permanent reference stations network. The main factor limiting the range extension of the RTK technique beyond a few tens of kilometers is the differential ionospheric correction between the roving and the nearest reference GNSS station. Such ionospheric correction prevents the real-time ambiguity fixing, and therefore the corresponding accurate navigation at sub-decimeter level. The ionosphere produces ambiguity biases and correlations whose mitigation becomes the main problem to sort out. Even with the aid of multi-reference-station techniques, due to the baseline limitation (<20 km), several thousands would be required to cover such a service to the whole European region.<ref>[http://www.gsa.europa.eu/wartk-based-egnos-and-galileo-technical-feasibility-study WARTK-EGAL Project]</ref>
 
During the last few years, the group gAGE/UPC has developed the so-called Wide-Area Real-Time Kinematics (WARTK) technique, which allows the extension of local services based on the real-time carrier phase ambiguity resolution to wide-area scale (i.e. baselines between the rover and reference stations greater than 100 km), for both dual-frequency (GPS) and 3-frequency systems (Galileo and modernised GPS). The Wide-Area Real-Time Kinematics (WARTK) technique for dual and 3-frequency systems are based on an optimal combination of accurate ionospheric and geodetic models in a permanent reference stations network. The main factor limiting the range extension of the RTK technique beyond a few tens of kilometres is the differential ionospheric correction between the roving and the nearest reference GNSS station. Such ionospheric correction impedes the real-time ambiguity fixing, and therefore the corresponding accurate navigation at sub-decimetre level. The ionosphere produces ambiguity biases and correlations whose mitigation becomes the main problem to sort out. Even with the aid of multi-reference-station techniques, due to the baseline limitation (<20 km), several thousands would be required to cover such a service to the whole European region, obviously unaffordable from a logistic and economic point of view.


The main techniques supporting WARTK are related to an accurate real-time computation of ionospheric corrections, combined with an optimal processing of GNSS observables (carrier phases in particular) in both 2 and 3-frequency systems. The method increases the RTK/NRTK service area, with permanent stations separated by up to 500–900 kilometers — all while requiring 100 to 1,000 times fewer receivers covering a given region.<ref> Hernández-Pajares et al, ''Feasibility Study of a European Wide Area Real Time Kinematic System,'' invited talk in 4th ESA Workshop on Satellite Navigation User Equipment Technologies (Navitec), ESTEC, Noordwijk, The Netherlands, December 2008</ref>


Although its feasibility has been demonstrated with real data, no WARTK operational system has been deployed so far.


==WARTK Related Articles==


The WARTK concept was introduced in the late 1990s to address these deficiencies. The method dramatically increases the RTK/NRTK service area, with permanent stations separated by up to 500–900 kilometers — all while requiring 100 to 1,000 times fewer receivers covering a given region.
The following articles include further information about different important topics related to a WARTK:
 
 
----------------------------
 
 
 
Used by high-precision navigation/surveying applications, based on the use of carrier phase measurements.
 
==WARTK Related Articles==


The following articles include further information about different important topics related to a Differential GNSS:
* [[WARTK Fundamentals|WARTK Fundamentals]] introduces the recently-developed WARTK technique.
* [[Work in Progress:DGNSS Fundamentals|DGNSS Fundamentals]] introduces the classical DGNSS technique, its functionalities and the objectives of a DGNSS system.


* The [[Work in Progress:DGNSS Standards|DGNSS Standards]] article summarizes the international bodies in charge of the standardization of DGNSS systems, the principle applicable documents and its current status.  
* The [[WARTK Standards|WARTK Standards]] article summarizes some conventions, models and formats commonly used by WARTK.  


* [[Work in Progress:DGNSS Systems|DGNSS Systems]] sections provides a brief overview of the current existing DGNSS systems.
* [[WARTK Systems|WARTK Systems]] sections provide an overview of the potential WARTK systems and applications.


==Notes==
==Notes==

Latest revision as of 17:13, 18 September 2014


FundamentalsFundamentals
Title Wide Area RTK (WARTK)
Edited by GMV
Level Basic
Year of Publication 2011
Logo GMV.png

In Real Time Kinematics (RTK), the compensation of the ionospheric delay between the base station and each of the roving users works for baselines up to 10-20 kilometers. When using a network of base stations, Network RTK (NRTK), to mitigate atmospheric dependent effects over distance, the allowed distance between baselines and rovers increases up to 50-70 kms. In the late 1990s, the Wide Area RTK concept was introduced by the Research Group of Astronomy and Geomatics (gAGE) from the Technical University of Catalonia (UPC) to address these problems.

Wide-Area Real-Time Kinematics (WARTK)

Starting in late 90's until nowadays, the group gAGE/UPC has developed the Wide-Area Real-Time Kinematics (WARTK) technique, which allows the extension of local services based on the real-time carrier phase ambiguity resolution to wide-area scale (i.e. baselines between the rover and reference stations greater than 100 km), for both dual-frequency (only GPS) and 3-frequency systems (also with Galileo and modernized GPS). The Wide-Area Real-Time Kinematics (WARTK) technique for dual and 3-frequency systems are based on an optimal combination of accurate ionospheric and geodetic models in a permanent reference stations network. The main factor limiting the range extension of the RTK technique beyond a few tens of kilometers is the differential ionospheric correction between the roving and the nearest reference GNSS station. Such ionospheric correction prevents the real-time ambiguity fixing, and therefore the corresponding accurate navigation at sub-decimeter level. The ionosphere produces ambiguity biases and correlations whose mitigation becomes the main problem to sort out. Even with the aid of multi-reference-station techniques, due to the baseline limitation (<20 km), several thousands would be required to cover such a service to the whole European region.[1]

The main techniques supporting WARTK are related to an accurate real-time computation of ionospheric corrections, combined with an optimal processing of GNSS observables (carrier phases in particular) in both 2 and 3-frequency systems. The method increases the RTK/NRTK service area, with permanent stations separated by up to 500–900 kilometers — all while requiring 100 to 1,000 times fewer receivers covering a given region.[2]

Although its feasibility has been demonstrated with real data, no WARTK operational system has been deployed so far.

WARTK Related Articles

The following articles include further information about different important topics related to a WARTK:

  • The WARTK Standards article summarizes some conventions, models and formats commonly used by WARTK.
  • WARTK Systems sections provide an overview of the potential WARTK systems and applications.

Notes


References

  1. ^ WARTK-EGAL Project
  2. ^ Hernández-Pajares et al, Feasibility Study of a European Wide Area Real Time Kinematic System, invited talk in 4th ESA Workshop on Satellite Navigation User Equipment Technologies (Navitec), ESTEC, Noordwijk, The Netherlands, December 2008