No matter which current technology you decide to employ, RTK-enabled devices are still unmatched in terms of precision. Even when you compare them to drones or survey robots that can help take measures in vast landscapes, RTK has remained both more reliable and accurate than anything else.
At this time, it is an indispensable type of technology for surveyors, which helps you attain measurements with unparalleled accuracy. There are two main methods that are currently used for obtaining RTK corrections for surveying. One is with your own base station, and the other is using an NTRIP service.
Whichever way you decide to go between these two, you are guaranteed near-perfect results. But you still have to be aware of each method's limitations and advantages before you decide on one. For that reason, we want to help and explain the differences between the two and to help you with your future choice.
What is an RTK Network?
RTK positioning is a satellite navigation technique that is used to enhance the accuracy of data collected from GNSS receivers. It collects and compares the signals from the fixed base station and satellites and compares them together. That way, RTK can provide centimeter-level accuracy in real time.
An RTK network actually expands the traditional setup by using multiple base stations that are interconnected with each other within a network infrastructure. These base stations collaborate with each other and provide correctional data that can be used across a wide geographical area.
The interconnected RTK network, which communicates across multiple base stations, along with comparable receivers, allows for easy correctional data between base stations.
A typical RTK setup consists of two devices, a rover and a base station, but it also requires a communication link between them.
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A rover is a mobile GNSS receiver used for data collection. It captures satellite signals, which help it to determine the precise location on Earth.
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A base station is a static GNSS receiver. It transmits both GNSS data from the satellites and its own position (correction data or corrections) at the same time.
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A communication link is used to connect the base station and rover. It does so either via radio or the internet using NTRIP (Networked Transport of RTCM via Internet Protocol).
However, there is also a way for you to get centimeter-level precision and not using your own local base. A single GNSS receiver can act as a rover if you configure it as such. It is also possible to do it using an NTRIP service, where corrections are received through a nearest third-party base.
How to Get RTK Corrections with Your Own Base Station?
Using your own base stations is always preferable in areas where internet connection is limited. It allows you to do things autonomously while getting corrections from a base over a long-range or a UHF radio. The advantage of a local base station is that you also have full control of its position, which means that you can achieve even greater accuracy.
Unfortunately, additional setup is required, and you are going to be losing time on getting everything in order. When you include the receiver, a tripod for the base, and a LoRa antenna for both the base and the rover, it results in a lot of surveying equipment that you have to set up. Also, LoRa has a limited baseline and can be largely dependent on the conditions of the environment you are working in.
To start things off, you need to position a GNSS receiver and the base station at a fixed position. The base station collects data from the satellite and transmits it, as well as its own position, to the rover. The signals are corrected from the base in real time, fixing errors and calculating a centimeter-level accuracy all at the same time.
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Base setup: Position a base at a point of known coordinates. Sometimes, it is not necessary to tie your coordinates to a real geographical position, and in that case, you don’t need to place the base over known coordinates.
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Initialize and transmit: The base station receives the signals and transmits them along with its own position. The data can be delivered to a rover via radio or using an NTRIP caster.
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Receiving and applying corrections: Set up your rover and begin collecting points or stake-out.
How to Get RTK Corrections with an NTRIP Service?
NTRIP service is a network of ground-based reference stations that contain precisely known locations. They work as GNSS receivers and are able to provide you with real-time correction data. To work properly, it requires a NTRIP client, usually a GNSS rover connected to the internet, a NTRIP server, the source of the correction data from all reference stations in the network, and a NTRIP caster, which is a caster that performs the role of an intermediary between the server and the NTRIP client.
If you use a NTRIP service, you don’t require a local base station to work in the RTK mode. There are state and commercial NTRIP services that are used for getting GNSS corrections. The good thing about it that it will help you reduce application costs and the setup is easy to do. However, it is dependent on the quality of the internet connection, and you also require a working cellular connection or at least a Wi-Fi modem.
To start using it, you first have to subscribe to a local NTRIP service for the area. Since a global NTRIP service does not exist, the available ones vary in accuracy, availability, and cost. Once you are subscribed, you are going to do the following:
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Connect the rover to the internet: Connect the NTRIP service to your rover using a SIM card or Wi-Fi.
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Set up your rover: Configure your RTK settings by connecting your receiver and picking a satellite system.
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Connect to the NTRIP service: Pick NTRIP as preferred correction input and add the details of your NTRIP provider.
Base Station or NTRIP Service?
Both methods are good and bad in their own way. Using a base station is preferable in situations where you require the highest accuracy possible. You have complete control of the data collection process and can operate independently from any of the external correction services. Also, base station surveying with LoRa is the best solution in areas with limited internet access.
On the other hand, NTRIP services are perfect if you are working in an urban area and the internet connection is guaranteed. You are also not going to be carrying a lot of GNSS equipment. It is also a good option in situations where scalability is not possible.
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Wrapping Things Up
There you have it, two methods that enable RTK corrections. Both have their advantages and disadvantages, but the main one has to be the usage of internet connection. NTRIP does sound very useful and is a perfect choice when working in urban areas where internet connection is guaranteed. However, you are sacrificing accuracy in that way.
On the other hand, base station corrections are more reliable and you get better accuracy. Unfortunately, you will need to carry a lot of equipment with you all the time. Also, while a paid subscription is not needed, a high initial cost is something that you will need to deal with.
Either way, both methods are equally useful, just depending on your line of work, project or preference. We suggest determining the main needs of your project and then starting from there when picking a desirable RTK correction method.
FAQs
A few most asked questions for the end.
What is RTK and why is it important for surveying?
RTK, or Real-Time Kinematic, is a satellite navigation technique that corrects common errors in GNSS (Global Navigation Satellite System) signals to achieve centimeter-level accuracy. It is crucial for professional surveyors as it provides highly precise and reliable location data in real-time, which is essential for tasks like construction staking, land mapping, and infrastructure development.
How does a local base station work?
A local RTK setup consists of a base station and a rover. The base station is a static GNSS receiver placed at a fixed point. It continuously tracks satellite signals and calculates the error between its known, precise location and the location determined by the satellite signals. It then broadcasts this correction data via a radio link (like LoRa or UHF) to the rover, which applies these corrections to its own measurements to determine its precise position.
What is an NTRIP service?
NTRIP (Networked Transport of RTCM via Internet Protocol) is a service that streams RTK correction data over the internet. It utilizes a network of interconnected base stations spread over a wide geographical area. A user's rover connects to a central NTRIP caster via the internet (using a SIM card or Wi-Fi) to receive correction data from the nearest reference station in the network, eliminating the need for a personal base station.
Which method is more accurate, a base station or NTRIP?
A local base station setup generally offers higher accuracy. Because you can place the base station closer to your work area (a shorter baseline), the atmospheric conditions between the base and rover are more similar, leading to more precise corrections. NTRIP services often rely on reference stations that are further away (longer baselines), which can slightly reduce accuracy.
