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How can we use satellite signals to achieve millimeter-level accuracy? What is the mysterious power behind RTK technology?
In today's society, precise positioning technology is ubiquitous, from self-driving car systems to agricultural machinery, all rely on this technology. Even a positioning accuracy of a few millimeters plays an important role in many applications. The birth of Real-Time Kinematic (RTK) makes all this possible, using satellite signals to achieve millimeter-level precise positioning. What incredible technologies are hidden behind this?
Basic concepts of RTK technology
RTK technology is an application that performs measurements by correcting common errors in current satellite navigation (GNSS) systems. It utilizes phase measurements of the signal’s carrier wave, rather than just the signal content itself, and relies on a single reference station or interpolated virtual stations to provide real-time corrections to achieve centimeter-level accuracy.
RTK is affected by many different factors, including how accurately the receiver electronics processes the satellite signals, as well as various error sources such as unmitigated ionospheric and tropospheric delays, signal multipath, satellite clock and ephemeris errors, etc.
Signal Propagation and Phase Tracking
Understanding how satellite signals propagate is critical to accurately calculating position. RTK uses a fixed base station receiver and a mobile device. Based on the signal carrier phase observed by the base station, the mobile device performs a comparison to correct its own position error.
Using this technology, RTK systems are able to improve positioning accuracy within a range of about 20 kilometers from the base station, although the absolute position accuracy of the mobile device remains the same as the calculated position of the base station.
Business Application and Technical Architecture
RTK technology has a wide range of applications, including land surveying, hydrological surveying, and unmanned aerial vehicle navigation. The technology typically relies on a base station receiver and multiple mobile units, with low-cost real-time signal transmission via wireless modems in the UHF band.
Even so, RTK technology remains limited for some navigation uses, but it shows unparalleled potential in roles such as surveying and precision agriculture.
CORS and Virtual Reference Networks
With the further development of technology, the establishment of a continuously operating reference station (CORS) network has greatly improved the accuracy of RTK. This network consists of multiple base stations that can send messages simultaneously, reducing the errors that may occur in a single base station. Through the Virtual Reference Network (VRN), accuracy can be increased without using base stations.
SummaryOverall, the development of RTK technology has not only changed the surveying industry, it has also profoundly affected transportation, agriculture, and many high-tech fields. This technology allows us to know our location with millimeter-level accuracy, paving the way for future applications. However, what will be the next development?
