Avaliação da precisão e acurácia do posicionamento de máquinas agrícolas a partir do GNSS na região oeste do Paraná

Abstract

This work compares the main positioning methods used in Precision Agriculture: RTK (Real Time Kinematic), autopilot without signal corrections and manual driving. The first experiment evaluated the precision and accuracy using autopilot without signal corrections and manual driving, and related to the ionospheric indices S4 and ROTI. The results indicated that manual driving is less precise and accurate than autopilot driving (without signal corrections), regardless of the time of day. As an example, in the morning, manual driving presented the worst results (σ = ± 0.463 m and RMSE = 0.501 m), while autopilot already presented the best results (σ = ± 0.035 m and RMSE = 0.037 m). Knowing that the autopilot performs positioning by GNSS, there was a worsening of precision and accuracy in the afternoon (RMSE = 0.051 m) and at night (σ = ± 0.036 m, RMSE = 0.041 m), a fact corroborated by the moderate ionospheric activity in the region: S4 from 0.4 to 0.6 and ROTI close to 0.02 ROT/s. The second experiment consisted of considering the STSH geodetic station, belonging to the INCT GNSS-NavAer network and located at the top of the N block of UTFPR Campus Santa Helena, as an immobile tractor and performing the positioning by RTK. For this, the RTKLib software (GPS and GLONASS constellations and L1/L2 carriers) was used, for three dates in 2023 (contemplating seasonal variation) and three different base stations (varying the length of the baselines). Having estimated the Cartesian coordinates X, Y, Z and local e, n, u, and knowing the tractor coordinates, precision and accuracy were calculated for all scenarios. The best values were obtained for the day of low ionospheric activity (05/16/2023), regardless of the length of the baseline considered: for example, considering the ITAI base (located in Foz do guaçu/PR, 68 km from the tractor ), in the morning the mean value was σ = ± 0.035 m and RMSE = 0.148 m, in the afternoon it was σ = ± 0.046 m and RMSE = 0.113 m, and at night it was σ = ± 0.052 m and RMSE = 0.097 m . The worst values were identified for 03/21/2023 (autumn equinox), when strong irregularities and ionospheric scintillations occurred, and precision and accuracy degrade as the baseline increases, as for example for the MSMN base (located in Mundo Novo/MS, 102 km from the tractor), which presented an average value of σ = ± 13.389 m and RMSE = 14.9946 m, while ITAI presented σ = ± 9.822 m and RMSE = 10.907 m. The RTK positioning method presented results similar to the autopilot (without signal corrections) in periods of weak ionospheric activity. Base stations with distances greater than 60 km were used, due to the lack of active stations in the region of Santa Helena. Shorter baselines are expected to provide better results.