GNSS receivers use RTK(Real-time kinematic) to achieve sub-centimeter accuracy in positioning. If you’re interested in this technology, you’ll want to ensure you know what to expect. Here are some basics about RTK:
GNSS receivers use RTK to get sub-centimeter accurate positioning:
Typically, GNSS receivers have sub-meter accuracy, which is needed for land surveying. However, many mobile devices are capable of obtaining raw GNSS measurements that can use for improved positioning. These are often called pseudoranges. These are usually used for low-precision real-time positioning.
Besides pseudoranges, other techniques can increase the accuracy of a position. These include carrier-phase measurements, code-based measurements, and phase-phase combinations. All these methods can use to improve positioning. But the data quality depends on the service provider and the accuracy required.
Another technique is to combine code and carrier-phase observations, which can help to minimize the effects of ionospheric delay. The accuracy of these techniques depends on the signal frequencies and the quality of the error models. These techniques estimate the ionospheric effects, but they can only partially remove them.
Several manufacturers are currently producing finished RTK GNSS receivers. These are being sold to price-sensitive markets. These products are priced less than their counterparts made by leading brand-name companies. This trend has put tremendous pressure on existing brand-name receivers. It isn’t easy to convince buyers that their products are worth their premium. It has led some manufacturers to set up distribution in North America.
The post-processed kinematic technique works like RTK but without a real-time connection:
Using Post-Processed Kinematic (PPK) to improve GPS positioning accuracy is a technique that uses post-flight corrections to correct skewed data. The method is appropriate for various applications, including surveying, remote locations, and areas with no cellular coverage.
PPK corrects data skewed by ionospheric delays, multi-path interference, and weather conditions. It is ideal for many applications but beneficial for determining accurate orthometric heights in real-time.
Unlike PPK, Real-Time kinematics (RTK) does not require a real-time connection between a base station and a rover. However, this method is much faster and offers greater accuracy than PPK. In addition, the RTK method increases the range of possible positions. Depending on the geographic location, it can produce results as accurately as centimeters.
Using RTK is fast and safe. It allows for centimeter-level positioning, which is essential when working in challenging terrain. In addition, RTK reduces common errors between a base station and a roving station. These errors include ionospheric delays and satellite clock errors.
The best results are obtained for a more robust solution by using a large constellation of satellites and multi-frequency receivers. The solution is verified against a second-best candidate. It can take less than 10 seconds to find the correct solution. It is because the data from the receiver is processed by an algorithm, which reduces the amount of noise. The results are digital and can be easily converted into a GIS format.
To achieve maximum accuracy, a geoidal model must be used. Several models are available, but the latest one is the most accurate for calculating orthometric heights in real-time. The second benefit of this method is that it eliminates the need for ground control points, which can be time-consuming to obtain.
The RTK method is suitable for various applications, but it has limitations. In addition, the technique’s range includes errors from ionospheric delays, which can be corrected automatically. It is also not ideal for a long job, especially when it involves challenging terrain.
Work performed related to Real-time kinematic:
An RTK system consists of a stationary base station and a moving rover. The fixed base station has to be in a known location, while the rover has to be in a position where it can track GNSS signals continuously. Once the base station and the rover are in their respective positions, they should be set up to receive corrections. These corrections are transmitted from the fixed base station to the moving receiver. The receiver can calculate its position using the carrier phase measurement technique.
A typical GNSS receiver can determine its position to a few meters. However, higher accuracy is required for applications such as cadastral surveying and CAD drawing. A multi-frequency receiver recommended if the position is to be surveyed on the ground. These receivers can determine their position to almost as good a level as the number of satellites. They are also faster than GPS-only systems from Bench Mark, so better to check them out.
Unlike conventional one-to-one RTK, the proposed framework can achieve reliable performance with limited GNSS satellites in view. The success rate of the integer ambiguity resolution increases as more GNSS constellations are added to the RTK network.
The real-time kinematic method is another technique that improves GNSS data’s accuracy. This method produces the most positions in the least amount of time. It is based on a carrier phase measurement technique, where the signal’s phase from a satellite to a receiver is measured. It uses the refined delta positions from these carrier phase measurements to remove positional jumps, reduce noise levels, and improve the coordinates’ accuracy. Its accuracy is further enhanced by using a geoid model to calculate orthometric heights.
In this technique, two master agents could see up to 10 satellites in total, while a non-master agent could only see five. This strategy has been proven to work for various topographic surveys, including open-pit mining, precision farming, and land-deformation monitoring. The system has also been used in civil engineering and utility industries.