Two-Way Time Transfer Base Station for Rover Positioning
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Solution Overview
Problem
GNSS receivers, such as GPS or GLONASS, face accuracy degradation in position determination due to signal obstructions like trees and man-made structures, which is particularly challenging for small rovers like golf carts, as existing solutions are costly and complex.
Innovation Solution
A fixed base station broadcasts an RF signal modulated with a pseudo-random code synchronized with GPS time, serving as a ranging signal for rovers, even in areas with limited satellite visibility, and uses Two-Way-Time-Transfer to enhance position determination accuracy, allowing rovers to calculate their position with fewer satellite signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GNSS receivers rely solely on satellite signals for position determination, then the system structure remains simple, but position accuracy degrades in areas with signal obstructions like trees and man-made structures
Solution Approach 1:
The patent introduces a base station as an intermediary component that transmits pseudorandom ranging signals to rovers. This base station acts as a mediator between the satellite system and the rover, providing an additional ranging source that operates independently of satellite signal obstructions. The base station's transmitted signal serves as a reliable reference for position determination in areas where satellite signals are blocked by trees or man-made structures.
2Measurement precision
If laser-based systems are used to improve position accuracy, then measurement precision improves, but device complexity and cost increase significantly
Solution Approach 1:
The patent employs inexpensive pseudorandom code sequences as the ranging signal mechanism, replacing expensive laser-based systems. The pseudorandom codes are generated and transmitted using standard RF communication equipment, making the system cost-effective and suitable for widespread deployment in applications like golf course management where multiple rovers need positioning capability.
3Reliability
If rovers require signals from four satellites for complete position determination, then position accuracy is maintained, but the system becomes vulnerable to signal obstruction
Solution Approach 1:
The patent implements a preemptive measure by establishing base stations in advance at strategic locations. These base stations are positioned to provide coverage in areas where satellite signals are likely to be obstructed. The base stations continuously transmit ranging signals, ensuring that rovers always have access to sufficient ranging sources (satellites plus base stations) to maintain reliable position determination even when satellite signals are blocked.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution improves position accuracy by providing a terrestrial ranging source, reducing errors in height and clock estimation, and enabling accurate height determination, which is beneficial for applications like earth excavation and road paving, while being cost-effective and easier to implement compared to laser-based systems.
Implementation Method 1
a fixed base station, which has a known position, broadcasts to the rovers an RF signal that is modulated with a pseudo-random code
Implementation Method 2
The base station and rovers may also or instead transmit and receive wider baseband radio signals, such as WiFi (OFDM) and Ultra Wide Band (UWB) signals, for increased accuracy and a reduction in the adverse effects of multipath signals
Data Source
AI summary
A system for enhancing location estimates by movable rovers including one or more base stations that engage in two way time transfer (TWTT) with the rovers. Each TWTT operation between a given base station and a given rover provides range measurements and clock differences between the base station and rover. The range measurements are based on the travel time of return TWTT signals and the clock differences are based on a phase offset of a code in the return TWTT signal and/or timing information included in the return TWTT signals.