RTK networks are increasingly common, but it’s important to realize that not all of them operate using the same technology. In fact, two networks can function in entirely different ways, which can have a significant impact on your work in the field. In the following article and video, we’ll explore these two types of networks, how they operate, and what the differences mean for you.
Overview of Surveying Networks
Virtual Reference Station (VRS) Networks
Applications of P2P and VRS Networks in Surveying
Surveying technology has advanced significantly over the past few decades, largely driven by the demand for greater accuracy, efficiency, and reliability. Two of the most popular techniques in modern geodetic surveying are Point-to-Point (P2P) networks and Virtual Reference Station (VRS) networks. Both methods leverage the power of RTK, but they differ in terms of their working principles, required technology, and applications.
In this comprehensive article, we’ll explore the differences between Point-to-Point (P2P) and VRS networks, explain how each works, the technology required, and weigh the pros and cons of each method. Additionally, we’ll discuss their common applications, which will help surveyors choose the best system for their needs.
With RTK one constant that will always be required is a base station (unless the military decides to open up their encrypted signals). For surveyors, that has often meant bringing their own base and running a base and rover type setup. However, within the last 15 years, more and more companies have begun to adopt network rovers, where instead of having their own base, they subscribe to a service that provides access to nearby base stations over a cellular network. As I mentioned earlier, not all of these networks were created using the same technology. Typically, one of two NTRIP (Network Transport of RTCM via Internet Protocol) methods are used in commercial networks; Point-to-Point or VRS (Virtual Reference Station).
How P2P Networks Work
A Point-to-Point (P2P) network, also referred to as a Real-Time Kinematic (RTK) network, is a traditional method of GNSS-based surveying. This technique involves the use of two main components:
A Point-to-Point solution works much in the same way a UHF base and rover setup works. A base station remains stationary and records satellite signals from GNSS satellites. It calculates the error between its known coordinates and the satellite-provided coordinates. These correction data are transmitted to the rover, which then adjusts its own measurements based on these corrections, allowing it to calculate a more accurate position. The distance between the base station and the rover is critical, as the accuracy of corrections diminishes with increased distance. Examples include Bench-Mark’s StormCaster service, Carlson’s Listen-Listen and SNIP Caster.
Technology Required for P2P Networks
Advantages of P2P
Disadvantages of P2P Networks
2. Switching Base Stations: As you have to connect directly to a base station, if you are moving between areas, you will have to switch to a different base station. This means you have to know the best station for your area.
How VRS Networks Work
A Virtual Reference Station (VRS) network is a more advanced surveying technology that builds on the traditional RTK (P2P) approach but eliminates many of its limitations. In VRS networks, instead of relying on a single base station, a network of permanent reference stations is installed across a geographic area. These stations continuously collect satellite data and send it to a central processing unit.
When a rover in the field requests correction data, the system generates a “virtual” base station, positioned near the rover. The virtual station is designed to provide correction data that accounts for local conditions, leading to high accuracy, even over long distances. Examples include Leica’s Smartnet and Trimble’s Cannet.
Technology Required for VRS Networks
Pros of VRS Networks
Efficiency: VRS networks reduce the need for moving and setting up base stations, which saves time and increases productivity.
Wide Coverage Area: VRS networks can provide accurate GNSS corrections over large areas, covering hundreds or even thousands of kilometers.
No Need for Local Base Stations: Since VRS networks use multiple fixed reference stations, there’s no need to set up a dedicated base station for each project. The virtual base station is automatically created near the rover’s location.
Cons of VRS Networks
1. Higher Initial Costs: Establishing a VRS network requires a significant investment in infrastructure, including multiple reference stations, a central server, and communication links.
3. Maintenance and Management: Managing a VRS network involves maintaining the reference stations, communication links, and central server. This can be complex and costly.
4. High Subscription Fees: Accessing a commercial VRS network often requires a subscription, which adds to the operational cost for surveyors. This can cost upwards of $3,500 a year.
Common Applications of P2P Networks
Common Applications of VRS Networks
Both Point-to-Point (P2P) and Virtual Reference Station (VRS) networks play important roles in modern surveying. While P2P networks offer simplicity and high accuracy over short distances, they struggle with range limitations and require line-of-sight communication. VRS networks, on the other hand, provide broader coverage but come with higher initial and operational costs.
Surveyors must weigh the pros and cons of each method based on the scale, budget, and geographic conditions of their projects. For small, localized jobs, P2P may be the most practical and cost-effective solution. However, for large-scale, geographically dispersed surveys, VRS networks offer superior performance and efficiency. Understanding the strengths and limitations of both systems will help surveyors make informed decisions and ensure the success of their projects.
The primary difference lies in how they provide correction data. P2P networks rely on a single base station to transmit corrections to a rover within a limited range. In contrast, VRS networks use a network of reference stations to create a virtual base station near the rover, allowing for greater coverage and accuracy over large areas.
P2P networks are simple to set up, cost-effective for small areas, and provide high accuracy over short distances (typically within 20–25 km). They require only one base station and one rover, making them ideal for smaller projects like boundary and topographic surveys.
The main disadvantages of VRS networks include higher initial setup costs, complex infrastructure management, and ongoing subscription fees for access to the network. Additionally, maintaining the network’s reference stations and central processing server can add to operational costs.
The main disadvantages of VRS networks include higher initial setup costs, complex infrastructure management, and ongoing subscription fees for access to the network. Additionally, maintaining the network’s reference stations and central processing server can add to operational costs.
P2P networks are more suitable for smaller projects that cover a limited area, such as construction site surveys, topographic surveys, and boundary mapping. They are a cost-effective solution when the survey area is within the base station’s range, typically under 25 km.
Bench Mark Equipment & Supplies is your team to trust with all your surveying equipment. We have been providing high-quality surveying equipment to land surveyors, engineers, construction, airborne and resource professionals since 2002. This helps establish ourselves as the go-to team in Calgary, Canada, and the USA. Plus, we provide a wide selection of equipment, including global navigation satellite systems, RTK GPS equipment, GNSS receivers, and more. We strive to provide the highest level of customer care and service for everyone. To speak to one of our team today, call us at 403-286-0333 or email us at [email protected].
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