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|Year of Publication||2011|
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.
As WARTK is based on RTK, the same standards applied in RTK could be applicable to WARTK. The main difference is that the ionospheric delay is not assumed to be the same as the reference station but it is broadcasted to the users, implying additional messages. This ionospheric delay is computed in a CPF using a real-time model of ionosphere. The main features of the WARTK technique for dual-frequency and three-frequency data are patented:
- Wide Area RTK (WARTK), in 1999. UPC-Patent Nbr.992585.
- WARTK for 3 frequencies (WARTK-3), in 2002. ESA Patent Nbr.02-12627.