Wide-Area GNSS Corrections for Precise Positioning and Navigation in Agriculture

Abstract

This paper characterizes, with static and roving GNSS receivers in the context of precision agriculture research, the hybrid ionospheric-geodetic GNSS model Wide-Area Real-Time Kinematics (WARTK), which computes and broadcasts real-time corrections for high-precision GNSS positioning and navigation within sparse GNSS receiver networks. This research is motivated by the potential benefits of the low-cost precise WARTK technique on mass-market applications such as precision agriculture. The results from two experiments summarized in this work, the second one involving a working spraying tractor, show, firstly, that the corrections from the model are in good agreement with the corrections provided by IGS (International GNSS Services) analysis centers computed in post-processing from global GNSS data. Moreover, secondly and most importantly, we have shown that WARTK provides navigation solutions at decimeter-level accuracy, and the ionospheric corrections significantly reduce the computational time for ambiguity estimation: up to convergence times for the 50%, 75% and 95% of cases equal or below 30 s (single-epoch), 150 s and 600 s approximately, vs. 1000 s, 2750 s and 4850 s without ionospheric corrections, everything for a roving receiver at more than 100 km far away from the nearest permanent receiver. The real-time horizontal position errors reach up to 3 cm, 5 cm and 12 cm for 50%, 75% and 95% of cases, respectively, by constraining and continuously updating the ambiguities without updating the permanent receiver coordinates, vs. the 6 cm, 12 cm and 32 cm, respectively, in the same conditions but without WARTK ionospheric corrections.

Ionosphere over Eastern North Atlantic Midlatitudinal Zone during Geomagnetic Storms

“…RAEGE-Az provides data in the RINEX 3.0 format. These files were processed and calibrated using software developed by the UPC-IonSAT team [21,22]. This software allows the reading of RINEX 3.0 files to obtain an ionospheric (geometry-free) combination of dualfrequency carrier phases L1-L2, download satellites RINEX 3 broadcast ephemeris files in SP3 format to calculate non-calibrated slant TEC (i.e., affected by the carrier phase bias) from each of the available satellite and receiver, and to use UQRG GIMs to calibrate slant TEC and calculate vertical TEC, from dual-frequency carrier phase measurements only.…”