Which of the following statements regarding GNSS guidance systems used in precision agriculture is/are correct?
Options:
(A) Real-Time Kinematic (RTK) GNSS uses a local base station or cellular CORS network to achieve pass-to-pass accuracy within $\pm 2\text{ cm}$.
(B) Differential GPS (DGPS) utilizing satellite-based augmentation systems (SBAS, like WAAS or GAGAN) typically provides pass-to-pass accuracy of $15 - 30\text{ cm}$.
(C) Autonomous (unaugmented) single-receiver GPS typically exhibits positioning errors of $2 - 5\text{ m}$, which is inadequate for precision row-crop auto-steering.
(D) RTK-GPS requires direct optical line of sight between the tractor cab and satellites, and cannot function using radio frequency signals.
Answer Key:
A, B, C
Step-by-Step Solution & Explanation
• RTK uses carrier phase measurements and ground station telemetry to provide centimeter-level accuracy (A is correct).
• SBAS/DGPS code-differential correction yields sub-meter pass-to-pass tracking (B is correct).
• Standard autonomous GPS has drift errors up to 5 meters due to ionospheric delay (C is correct).
• RTK relies on microwave RF satellite signals and UHF/cellular telemetry, not optical line of sight (D is false).