Abstract
Recently, an accurate positioning has become the kernel of autonomous navigation with the rapid growth of drones including mapping purpose. The Network-based Real-time Kinematic (NRTK) system was predominantly used for precision positioning in many fields such as surveying and agriculture, mostly in static mode or low-speed operation. The NRTK positioning, in general, shows much better performance with the fixed integer ambiguities. However, the success rate of the ambiguity resolution is highly dependent on the ionospheric condition and the surrounding environment of Global Navigation Satellite System (GNSS) positioning, which particularly corresponds to the low-cost GNSS receivers. We analyzed the effects of the ionospheric conditions on the GNSS NRTK, as well as the possibility of applying the mobile NRTK to drone navigation for mapping. Two NRTK systems in operation were analyzed during a period of high ionospheric conditions, and the accuracy and the performance were compared for several operational cases. The test results show that a submeter accuracy is available even with float ambiguity under a favorable condition (i.e., visibility of the satellites as well as stable ionosphere). We still need to consider how to deal with ionospheric disturbances which may prevent NRTK positioning.
Highlights
The Global Navigation Satellite System (GNSS) is widely used for accurate positioning in various civil applications
It is generally known that the integer ambiguity resolution is essential for high-accuracy Networkbased Realtime Kinematic (RTK) (NRTK) solutions based on the carrier phase observations
Each R6 receiver is connected to a Virtual Reference Station (VRS) and a Flächen Korrektur Parameter (FKP) server to perform NRTK positioning, and the horizontal baseline vector was estimated to evaluate the performance of both systems
Summary
The Global Navigation Satellite System (GNSS) is widely used for accurate positioning in various civil applications. The stand-alone positioning using C/A code pseudoranges is the most popular approach for aviation and/or ground vehicle navigation. Rather than code-based GNSS positioning in either stand-alone or differential mode, the carrier phase observables are commonly used for precision geodetic and surveying applications where an accurate positioning is the most important consideration. A more accurate and stable positioning technique was first proposed in mid-1990 by rigorously modeling all error components based on a network of known references, called Networkbased RTK (NRTK) technique [1,2,3]. Even with the carrier phase observations, it is challenging to reach such an accuracy without proper integer ambiguity resolution. We analyzed the stability and the accuracy of NRTK systems under various conditions to verify the possibility of applying this to drone navigation. The reference stations of Korea are densely located ranging from 30 to 50 km for most of the baselines, which should be a worthy infrastructure for NRTK positioning
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