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The Wide Area RTK (WARTK) concept was introduced in the late 1990s by the [http://www.gage.es/ Research Group of Astronomy and Geomatics (gAGE)] from the Technical University of Catalonia (UPC). The WARTK method increases the RTK/NRTK service area, with permanent stations separated by up to 500–900 kilometers. RTK reference stations should be of the order of ten km distance from rover, because the ionosphere produces ambiguity estimation biases that lead to positioning error above 1 meter. The main [[WARTK Fundamentals|WARTK techniques]] 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 GNSS systems<ref>[http://www.gsa.europa.eu/wartk-based-egnos-and-galileo-technical-feasibility-study WARTK-EGAL Project]</ref>. Its potential use is in high-precision navigation/surveying applications.


The Wide Area RTK (WARTK) concept was introduced in the late 1990s by the [http://www.gage.es/ Research Group of Astronomy and Geomatics (gAGE)] from the Technical University of Catalonia (UPC). The WARTK method dramatically increases the RTK/NRTK service area, with permanent stations separated by up to 500–900 kilometers. RTK reference stations should be of the order of ten km distance from rover, because the ionosphere produces ambiguity estimation biases that lead to positioning error above 1 meter. The main [[WARTK Fundamentals|WARTK techniques]] 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 GNSS systems.
==WARTK Systems==
 
Currently, the WARTK concept has been not developed as an operational system, although some projects have been carried out showing its feasibility.<ref>M. Hernandez-Pajares, et al, ''Real-time integrated water vapor determination using OTF carrier-phase ambiguity resolution in WADGPS networks'', Proceedings of the Institute of Navigation, pp. 616-625, Salt Lake City, UT, 2000.</ref><ref>M. Hernandez-Pajares, et al. ''Wide Area Real Time Kinematics with Galileo and GPS Signals'', Proceedings of the Institute of Navigation, Long Beach, California, 2004.</ref>


==WARTK Systems==
[[File:WARTK2test.JPG|350px|thumb|WARTK-2 technique test in Europe.]]
[[File:WARTK2test.JPG|350px|thumb|WARTK-2 technique test in Europe.]]


User Receiver that can applied WARTK techniques are not still in the market. The gAGE/UPC group have been done several test with simulated data and also with real data. In the case of WARTK-3 the work has been done together with ESTEC/ESA, as simulated data from GALILEO constellation is needed. In the following, the most representative experiments carried with WARTK are described:
A typical implementation of a WARTK system could include the following components:
*A Reference Stations Network (RSN), composed of a set of multi-frequency GNSS receivers covering the service area separated a few hundreds of kilometers away. For a region like Western Europe, a few tens of receivers would be enough. The system could take benefit of already deployed stations, provided they met the needed technical and environmental requirements.
*A Central Processing Facility (CPF), connected to the reference station network with the capability to estimate the ionospheric correction with the required accuracy, and possibly with the function to re-distribute corrections from the reference stations to the users.
*An Internal Communication Subsystem (ICS), connecting the reference station network and the Central Processing Facility.
*A Broadcast Communication Subsystem (BCS), distributing the ionospheric corrections and the reference station data to the users.
*User receivers, able to receive the data and to apply the corresponding algorithms, according to the corresponding Interface Control Document.


*Test for WARTK-2 technique: Results during the recent Solar Maximum peak, with several European stations (see figure) during four consecutive days, 110-113 of 2000. In this scenario the geomagnetic activity is low to moderate, but the typical vertical Total Electron Content value at noon is 60 TECU (and STEC until 300 TECU and more), i.e. 3 times the values in 1998.
The final profile and complexity of the system could be highly affected by key characteristics, such as the requested level of reliability, availability, security or safety.


==Notes==
==Notes==

Latest revision as of 17:16, 18 September 2014


FundamentalsFundamentals
Title WARTK Systems
Edited by GMV
Level Basic
Year of Publication 2011
Logo GMV.png

The Wide Area RTK (WARTK) concept was introduced in the late 1990s by the Research Group of Astronomy and Geomatics (gAGE) from the Technical University of Catalonia (UPC). The WARTK method increases the RTK/NRTK service area, with permanent stations separated by up to 500–900 kilometers. RTK reference stations should be of the order of ten km distance from rover, because the ionosphere produces ambiguity estimation biases that lead to positioning error above 1 meter. The main WARTK techniques 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 GNSS systems[1]. Its potential use is in high-precision navigation/surveying applications.

WARTK Systems

Currently, the WARTK concept has been not developed as an operational system, although some projects have been carried out showing its feasibility.[2][3]

WARTK-2 technique test in Europe.

A typical implementation of a WARTK system could include the following components:

  • A Reference Stations Network (RSN), composed of a set of multi-frequency GNSS receivers covering the service area separated a few hundreds of kilometers away. For a region like Western Europe, a few tens of receivers would be enough. The system could take benefit of already deployed stations, provided they met the needed technical and environmental requirements.
  • A Central Processing Facility (CPF), connected to the reference station network with the capability to estimate the ionospheric correction with the required accuracy, and possibly with the function to re-distribute corrections from the reference stations to the users.
  • An Internal Communication Subsystem (ICS), connecting the reference station network and the Central Processing Facility.
  • A Broadcast Communication Subsystem (BCS), distributing the ionospheric corrections and the reference station data to the users.
  • User receivers, able to receive the data and to apply the corresponding algorithms, according to the corresponding Interface Control Document.

The final profile and complexity of the system could be highly affected by key characteristics, such as the requested level of reliability, availability, security or safety.

Notes


References

  1. ^ WARTK-EGAL Project
  2. ^ M. Hernandez-Pajares, et al, Real-time integrated water vapor determination using OTF carrier-phase ambiguity resolution in WADGPS networks, Proceedings of the Institute of Navigation, pp. 616-625, Salt Lake City, UT, 2000.
  3. ^ M. Hernandez-Pajares, et al. Wide Area Real Time Kinematics with Galileo and GPS Signals, Proceedings of the Institute of Navigation, Long Beach, California, 2004.
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