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| 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).
| | The '''Wide Area RTK''' concept was introduced in thelate 1990s to address RTK deficiencies by the [http://www.gage.es/ Research Group of Astronomy and Geomatics (gAGE)] from the Technical University of Catalonia (UPC). |
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| ==Wide-Area Real-Time Kinematics (WARTK)==
| | The WARTK 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. |
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| 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.
| | ==Wide-Area Real-Time Kinematics (WARTK) Fundamentals== |
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| 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 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.
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| The target market should be a market line where the enhancement provided by the WARTK technique is needed, such as sub-decimetre accuracy, orientation and wide-area service coverage. It would be mandatory to have institutional support due to the extended permanent receiver network involved to perform such techniques. The EGNOS RIMS network would be a feasible possibility and it would diminish the initial investment for the prototype. The time-to-market should be reduced to the minimum since the current GNSS systems, already on the market, could evolve in the direction of WARTK (e.g., cheaper dual-frequency receivers). The following markets have been identified as the most suitable for the different applications that WARTK is able to provide at this stage of development: accurate navigation in deep seas, tsunami detection, instant meteorology, civil construction, precision farming, orientation, cadastral coverage, real-time wide-area mapping and auto-piloting.<ref>[http://www.gsa.europa.eu/index.cfm?objectid=42B6F1B2-A906-2D88-C40D0B75612EDD2D WARTK-EGAL ESA Project WebPage]</ref>
| | ==WARTK Algorithms== |
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| ==WARTK Related Articles==
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| The following articles include further information about different important topics related to a WARTK:
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| * [[Work in Progress:WARTK Fundamentals|WARTK Fundamentals]] introduces the recently-developed WARTK technique.
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| * The [[Work in Progress:WARTK Standards|WARTK Standards]] article summarizes some conventions, models and formats commonly used by WARTK.
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| * [[Work in Progress:WARTK Systems|WARTK Systems]] sections provides an overview of the potential WARTK systems and applications.
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| ==Notes== | | ==Notes== |
