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VRS (virtual reference station)

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In the field of Global Navigation Satellite Systems (GNSS) and surveying, a Virtual Reference Station (VRS) is a technique used to enhance the accuracy and efficiency of Real-Time Kinematic (RTK) positioning. RTK is a method used to achieve centimeter-level accuracy in positioning by using carrier-phase measurements from GNSS satellites. However, RTK positioning can be affected by factors like distance from reference stations and signal obstructions. VRS addresses these challenges by creating virtual reference stations to improve the accuracy and availability of RTK positioning.

Traditional RTK Positioning:

In traditional RTK positioning, a rover receiver collects raw satellite measurements and sends them to one or more physical reference stations. These reference stations serve as fixed and known points with known coordinates, and they receive satellite signals from the same GNSS satellites as the rover. By comparing the rover's measurements with the reference station's measurements, the rover's position can be accurately determined in real-time.

Challenges with Traditional RTK:

While traditional RTK offers high accuracy, it has some limitations:

  1. Limited Coverage: The accuracy of RTK decreases with increasing distance from the reference station(s). Users located far away from reference stations may experience reduced accuracy.
  2. Signal Obstructions: Buildings, trees, and other obstacles can block or reflect satellite signals, leading to signal degradation and reduced accuracy.
  3. Insufficient Reference Stations: In remote areas or regions with limited GNSS infrastructure, there may not be enough physical reference stations to provide adequate coverage.

Virtual Reference Station (VRS) - How It Works:

VRS is designed to overcome the limitations of traditional RTK positioning by creating virtual reference stations based on a network of physical reference stations. The key steps in the VRS process are as follows:

  1. Network of Reference Stations: A network of physical reference stations is established in the survey area. These reference stations are distributed strategically to ensure good coverage.
  2. Real-Time Data Communication: The reference stations continuously collect raw satellite measurements and transmit them in real-time to a central processing server.
  3. Server-Based Processing: The central server processes the raw measurements from multiple reference stations and calculates corrections for atmospheric and other errors.
  4. Virtual Reference Stations: Based on the corrections calculated by the central server, virtual reference stations are created at locations where no physical reference station exists. These virtual reference stations have known coordinates and provide correction data for rover receivers in their proximity.
  5. Rover Receivers: The rover receivers receive correction data from nearby physical or virtual reference stations, allowing them to compute highly accurate positions in real-time.

Benefits of Virtual Reference Station (VRS):

VRS offers several advantages over traditional RTK positioning:

  1. Increased Accuracy: VRS provides higher accuracy even at greater distances from the physical reference stations.
  2. Improved Coverage: Virtual reference stations extend the coverage of the GNSS network, ensuring accurate positioning in areas without physical reference stations.
  3. Better Performance in Obstructed Areas: VRS can mitigate the impact of signal obstructions, as rover receivers can receive correction data from multiple reference stations, reducing the effect of blocked or reflected signals.
  4. Cost-Effectiveness: VRS reduces the need for additional physical reference stations, making it a cost-effective solution for expanding RTK coverage.

Conclusion:

Virtual Reference Station (VRS) is a technique used in Real-Time Kinematic (RTK) positioning to enhance accuracy and coverage. By creating virtual reference stations based on a network of physical reference stations, VRS provides more accurate positioning even at larger distances and in obstructed areas. This technology plays a crucial role in high-precision surveying, precision agriculture, construction, and other applications that require real-time, centimeter-level accuracy in positioning.