For better management of agricultural crops, new technologies have been developed in the field with the help of agricultural mechanization. Among them, the use of global satellite navigation systems (GNSS System) combined with automatic steering systems for agricultural machinery stands out.
The GNSS System is made up of different constellations of satellites, which aim to navigate and position points on the Earth's surface. We can mention as GNSS systems, the Global Positioning System (GPS) of the USA, the Global Navigation Satellite System (Glonass) of Russia and the BeiDou Satellite Navigation System from China.
This combination between the GNSS system and agricultural machinery guidance systems allows greater control of mechanized operations such as traffic, parallelism and repeatability in sowing, planting and application of inputs.
If there is a need for repeatability of planting lines, as in the case of sugarcane cultivation, the real-time kinematic relative positioning method - RTK (Real time kinematic) combined with the hydraulic autopilot would be the most suitable combination, due to the high quality of positioning it achieves, in the range of centimeters.
However, when handling does not require centimeter quality, methods and equipment that provide decimeter quality can be used, such as differential positioning (DGPS) in conjunction with electric autopilot. However, it is also possible to combine the electric autopilot with the correction provided by the RTK system, especially when a real-time DGPS correction is not available.
In this context, the Center for Geomatics and Precision Agriculture (NGAP), at the Faculty of Agricultural and Veterinary Sciences of Jaboticabal (FCAV), at Unesp, conducted an experiment to evaluate the quality of positioning provided by the RTK system combined with an electric autopilot , in the operation of opening furrows for the purpose of implementing a perennial crop.
The work was carried out on a piece of land, located in the interior of the state of São Paulo, during the furrowing operation for the purpose of implementing a perennial crop. In this operation, a John Deere navigation system, StarFire ITC GPS receiver and GreenStar 2 1800 monitor with RTK correction system were used, combined with an electric autopilot, also John Deere.
To evaluate parallelism and furrow spacing, planting furrows measuring approximately 200m in length were mapped. This mapping was carried out with a Topcon total station, model GTS701 with angular precision of 2" and linear precision of 2mm + 2mm/km. Equipment classified as high precision by the Topographic Survey Execution Standard NBR 13.133. The Irradiation method was used for planimetry and Trigonometric Leveling for altimetry.
It is noteworthy that curvature and atmospheric refraction corrections were applied to distance measurements. To correct refraction, temperature and pressure measurements were observed during distance measurement. To record temperature and pressure, a Labortherm-N mercury thermometer, model Skalenwert 1k (resolution of 1º C) and a Fischer barometer (resolution of 1mbar) were used.
The furrow spacing adopted at the time of the operation was 3,5m between the planting lines. For each line between lines, the average spacing and respective precision were determined. Based on the reference value of 3,5m for spacing, furrowing accuracy was determined. Analysis of variance was performed, comparing the spacing between lines of the sampled grooves. As the evaluated section was approximately straight (NE-SW orientation), a linear regression analysis was performed to verify whether the furrowing operation maintained this straight path (Figure 1).
Figure 1 - Graphical representation of the grooves mapped in the experiment
Source: Rosalen and Deghaid (2013).
Table 1 displays the results of the regression analysis, the data displayed indicates that the trajectory of the furrowing operation in the planting lines remained straight; therefore, all determined linear correlation coefficients are close to one. Also, another indicator of the quality of the furrowing trajectory was the average precision for the adjusted straight lines equal to (0,09 +/- 0,02) m, that is, there was a deviation from the trajectory of around 9cm.
Table 1 - Regression analysis results for mapped planting furrows
Planting lines | Linear correlation coefficient |
1 | 0,9999973 |
2 | 0,9999987 |
3 | 0,9999982 |
5 | 0,9999977 |
6 | 0,9999989 |
7 | 0,9999992 |
8 | 0,9999913 |
9 | 0,9999983 |
10 | 0,9999992 |
11 | 0,9999976 |
Media | 0,9999978 |
Planting lines
Linear correlation coefficient
1
0,9999973
2
0,9999987
3
0,9999982
5
0,9999977
6
0,9999989
7
0,9999992
8
0,9999913
9
0,9999983
10
0,9999992
11
0,9999976
Media
0,9999978
Source: Rosalen and Deghaid (2013).
Table 2 displays the results of the average spacing obtained for each of the planting rows. It is noteworthy that no significant difference (P < 0,05) was detected between the spacing values for each line, indicating that parallelism was maintained.
Table 2 - Results of the average spacing between planting lines for the mapped furrows
Between planting line | Average (m)1 | Standard deviation (m) |
1 | 3,59 | 0,02 |
2 | 3,58 | 0,02 |
3 | 3,48 | 0,02 |
5 | 3,59 | 0,05 |
6 | 3,46 | 0,03 |
7 | 3,53 | 0,04 |
8 | 3,54 | 0,04 |
9 | 3,52 | 0,02 |
10 | 3,55 | 0,05 |
11 | 3,43 | 0,02 |
Media | 3,53 | 0,02 |
Between planting line
Average (m)1
Standard deviation (m)
1
3,59
0,02
2
3,58
0,02
3
3,48
0,02
5
3,59
0,05
6
3,46
0,03
7
3,53
0,04
8
3,54
0,04
9
3,52
0,02
10
3,55
0,05
11
3,43
0,02
Media
3,53
0,02
Source: Rosalen and Deghaid (2013).
Also, in Table 2, it is observed that the average spacing found for the lines between the mapped grooves was (3,53 +/- 0,02) m, indicating an accuracy of 3cm, considering the reference value of 3,5. XNUMX m. In this way, an accuracy in the order of centimeters was obtained, as expected for RTK correction.
The results found in the experiment indicated that the furrowing operation, regarding the navigation of the agricultural machine, obtained adequate performance, since parallelism was maintained between each furrow and the desired spacing was achieved, with a residual error in the order of centimeters.
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