What is Real-Time Kinematic (RTK) Surveying? Application of Real-Time Kinematic(RTK)

What is Real-Time Kinematic (RTK) Surveying?

RTK surveying is a surveying technique that uses a real-time kinematic GPS receiver to provide centimeter-level accuracy. It is used in surveying and construction to obtain the most accurate position and elevation data possible.

RTK surveying is also known as differential GPS (DGPS) surveying. The technique was developed in the early 1990s and has become more popular in recent years with the increased use of GPS and the decreasing cost of the receivers.

RTK surveying is used for topographic surveys, engineering surveys, construction surveys, and many other applications.

RTK survey is also used to measure and map the real-time (or dynamic) position of a mobile device in three dimensions, using one or more satellites.

RTK survey can be regarded as a complement to RTK GPS, which makes accurate measurements of positions on the Earth’s surface for use with GPS receivers.

The accuracy of RTK is better than civilian GPS in some places due to use of less satellites and hence shorter time required for measurement.

RTK Survey History

The surveying industry has been using RTK survey for more than 15 years to collect data for precise mapping.

For example, RTK has been used to measure the precise distances between bedrock and tunnel supports.

In recent years, RTK has also become popular with private land surveyors who use the technique for precise mapping of privately owned property. In fact, today there are few private land surveyors who do not use RTK technology.

Components of Real-Time Kinematic (RTK) Survey

• Base Station- consists of a global positioning system receiver and antenna that are installed at a known location.
• Base Station Controller- receives input from the rover and controls the operation of the rover. The base station controller can also send commands to the rover to adjust its position relative to a datum.
• Rover- consists of a GPS receiver and antenna, typically mounted in a vehicle. The rover receives signals from the GPS satellites and communicates with the base station controller.

RTK Survey procedure

The steps involved are:

1. Place the base station antenna on a known point on a building or ground using an electronic level and compass.
2. Install a second antenna as far away as possible from the base station antenna
3. Configure the base station and rover receivers to use a minimum of twelve satellite signals to determine position.
4. Drive the rover to each GPS monument with the transceiver in airplane mode so it can receive signals from both antennas simultaneously
5. Record the monument readings.
6. You will get a Minimum of two monuments at each site and occasionally more depending on distance and line of sight to the base station/Reflector antenna.
7. Average the readings and these are your real-time positions.

Risks Involved in Real-Time Kinematic Survey

The major risks are:

1. The base station antenna should remain stationary while in use.
2. The base station antenna must be placed on a known point, such as a building corner or other suitably rigid object.
3. It is often necessary to take two separate survey jobs to precisely define one monument, requiring the base station and reflector to be switched repeatedly between the two jobs.
4. The base station antenna must be kept away from power lines and other fields producing strong radio signals. These sources of interference can interfere with the ability of the base station antenna to communicate with the satellites.
5. The base station antenna must be installed and operated according to any regulations applicable to your location, including federal and local laws.
6. The dangers of working on or near high-voltage power lines should always be treated seriously. In many locations, electrical shocks from power lines can cause permanent injury and even death.
7. You should always use a ground-fault circuit interrupter (GFCI) when working with electricity near water. GFCIs are available in portable and fixed versions that can be used to test for the presence of power before connecting your equipment to electrical outlets.
8. A base station antenna must be installed at least 5 meters above ground on a known point, such as a radio tower or building corner, for effective operation.

RTK Survey Accuracy

RTK provides an accuracy of approximately 50 cm horizontally and 1.5 cm vertically in optimal conditions.

As with all GNSS applications, RTK precision depends on the number of receivers used, the number of satellites being tracked, and the geometry between them.

When three receivers are used, the RTK survey can achieve accuracies of less than 2 cm horizontally and 0.4 cm vertically.

Compared with RTK in its previous status, RTK surveying has experienced a tremendous improvement since the development of Real-Time Kinematic (RTK) technology.

Not only could surveyors use two or three base stations to increase precision, they can also benefit from postprocessing data obtained through RTK to precisely calculate the location, especially if professional software packages are available.

In conclusion, RTK survey is a very precise surveying technique but it still has its drawbacks in GPS surveying.

However, it is almost impossible to avoid the existing errors that are present in GPS surveying. Therefore, both RTK and GPS technologies should be used in every survey campaign.

RTK Survey Advantages

The advantages have been listed below.

1. RTK survey can achieve high-precision measurement in 3D location measurement.
2. RTK uses very few satellites and hence it can be used to measure the rapid change of earth surface heights with short time due to its short cycle time.
3. It can be applied to the surveying of large construction sites, such as that for highways, bridges and tunnels where a large amount of surveying data needs to be gathered quickly and precisely.
4. It can be applied to the surveying of large areas (many kilometers) and where the number of surveyors is many, such as tunnels and deep-sea exploration and development.
5. RTK survey can be applied to the surveying of construction sites with limited access due to their remote location.
6. RTK can help in reducing the cost of data collection process as it reduces data collection time by using less than 2 satellites for position determination accuracy monitoring.
7. RTK can be easily accomplished by using off-the-shelf software.
8. RTK provides good navigation capabilities in the absence of a good terrestrial reference system.

RTK Survey Disadvantages

The disadvantages are:

1. Because it relies on the precise knowledge and accurate positioning of three satellites, it is difficult to obtain precise positioning data.
2. The accuracy of the measurements obtained through RTK depends largely on the number and geometry of the base stations used.
3. RTK relies on World Geodetic System 1984 (WGS84) datum for its calculations and thus variation in position will occur as a result of variations in datum when compared to a true Geographic Coordinate System.
4. RTK requires further improvement in the development of specific RTK software.
5. RTK survey is not ideal for measuring the vertical height differences between buildings and terrain.
6. Because of its low accuracy, more than 3 satellites are required to achieve an equally high level of precision.
7. The equipment required for installation and operation is expensive and if not maintained will increase the cost of surveying the survey area by many times, which may result in failure of trying to use it in a cost-effective manner.
8. It is not easily utilized in areas where radio interference occurs and it is not suitable for use in areas where terrestrial references are lacking.
9. In some surveying conditions disturbances affect the RTK signal, this results in large-amplitude fluctuations which are difficult to suppress whether on the horizontal or vertical axis.
10. Due to the two-dimension of a RTK base station, there is a limitation of using it in determining altitude values that exist in all directions.
11. The requirements of RTK base stations are very high, such as tough environment and not only needs to be wired with power but also needs to be linked with computers.

RTK Survey Challenges

The challenges are basically the main problems encountered. They are:

1. Interference from other radio signals or electrical equipment used in the same location may interrupt the RTK signal, causing loss of signal lock or signal offset.
2. Since the RTK system uses satellites as its primary source of information, it is susceptible to satellite availability and positioning errors.

There is also a risk that information provided by the base station may be inaccurate and interfere with the process of data collection.

3. The RTK system is sensitive to differences in local temperatures and to variations in the quality of the ground beneath it.
4. Changes to surveyors’ location, measurements, and equipment all affect the accuracy of RTK data, affecting other types of surveying systems such as GPS and laser-based surveys.
5. The accuracy of RTK may change over time depending on conditions such as solar activity (as reflected by changes in the amount of sun seen by the satellites).
6. The cost of RTK equipment is high, requiring significant investment for an individual to purchase and maintain an RTK system.
7. The requirement for line of sight means that RTK systems must be installed in a manner that does not block the view of the satellites from their receivers.
8. The limited amount of information provided by GPS satellites means that satellite geometry is strategically critical to obtain good precision from the system.

Errors in RTK Survey

Potential errors that can occur in RTK surveying:

• Errors in the position of the base stations
• Errors caused by the magnetic field of the earth and the sun between base stations
• The measurement errors due to hardware equipment that are used
• Errors caused by the atmospheric conditions
• Errors in the overall system configuration and software used
• Storms, wind, rain and other weather that may affect the performance of RTK surveying systems

RTK Survey Applications

RTK Survey is applied in:

Geodesy

RTK survey is used in Geodesy to establish the geographic coordinates of points.

Hydrology

In hydrology, RTK survey is used to measure water levels, flow velocity and discharge.

Oceanography

RTK Survey is used in oceanography to monitor sea level rise.

Geology

In geology, RTK survey is used to measure the subsurface location of rock formations, ore bodies and precious metal deposits.

Archaeology

In archaeology, RTK survey is used to collect subsurface information on the location and forms of burial sites and artefacts.

Surveying in disaster relief

RTK Survey is used to collect data in disaster relief, being able to quickly and efficiently provide information on the extent of damage, location of survivors and areas requiring further relief efforts.

Geomatics

RTK Survey is used in Geomatics to measure surface undulations of the earth’s surface caused by natural or human action.

Photogrammetry

In photogrammetry, RTK Survey is used for the generation of digital elevation models and ortho-images from aerial imagery collection (digital photography).

Military survey

RTK Survey is used in the military to provide accurate topographic maps of a large area underground without the need for heavy equipment or excavation.

Survey in earthquakes

RTK Survey is used after an earthquake to map and record data about its effects on buildings, objects, land and terrain.

Agriculture

In agriculture, RTK Survey is used to plan, design and manage the layout of irrigation systems, fertilizer placement, crop-rotation schedules, etc.

Architecture

In architecture, RTK survey is used to determine the precise position of constructs such as buildings.

In mining industry

RTK surveying improves in mining industry by reducing costs and increasing efficiency by making mining more effective.

Earth science

RTK Survey is used in Earth science to monitor the surface changes which occur in the long term.

Surveying in airports and on highways

RTK Survey is used on highways and airports to build accurate maps of the foundation of buildings, roads and other structures such as bridges and tunnels.

In meteorology

In meteorology, RTK survey is used to provide high precision measurements during rainstorms and windstorms.

Marine engineering

In marine engineering, RTK Survey is used to build accurate topographic maps of submerged areas

Geophysics

In geophysics, RTK Survey is used to measure the subsurface location of rock formations, ore bodies and precious metal deposits (pits).

FAQs

What is RTK surveying?

Real-time kinematics (RTK) is a surveying system that estimates relative locations in real-time utilizing two Global Navigation Satellite System (GNSS) antennas. RTK technology is used to detect and repair frequent mistakes in GNSS findings.

What are the applications of the RTK positioning survey?

RTK is primarily utilized for high-frequency construction applications such as cadastral surveys, drone navigation, and other construction operations.

What are the limitations of the RTK positioning survey?

RTK technology is not usable in maritime regions, lands with obstacles (trees, mountains, etc.), or projects that interfere with communication. The technique necessitates the use of a pre-surveyed base station with known coordinates.

What are the advantages of RTK positioning survey?

RTK technology is ideal for applications that require frequent position checking, such as in concrete pouring or building construction. The system can be particularly effective for automated mapping, land surveying, and design.

What are the types of RTK survey systems?

There are two basic types: standalone or base station RTK GPS surveyors and integrated RTK GPS systems.

Standalone GPS receivers are used with a separate antenna signal processor while integrated units utilize an internal differential module to achieve higher performance.

What are the limitations of integrated RTK GPS systems?

Integrated RTK GPS systems are less accurate than standalone systems and therefore more susceptible to error.

However, there are many circumstances in which the increased convenience of integrated units outweighs their limitations, such as real-time construction surveying.

How can errors in RTK survey be prevented?

The most significant source of errors occurs from the magnetic field of the earth and the sun between base stations and receivers. In the case of RTK, the main source of error is the earth’s magnetic field and solar radiation.

What is RTK rover?

RTK rover is a portable system that helps in high quality and accurate RTK surveying. It is used for surveyors and users who are restricted to a certain area for surveying. The system has been designed with advanced technology to ensure high accuracy.

What is RTK antenna?

RTK antenna is a small, lightweight device that measures GNSS radio signals from satellites and sends them to a base station or receiver with an antenna. This process is known as GNSS propagation.

What are the benefits of RTK rover?

There are many advantages of RTK rover. It can be used for field surveys, construction surveying, and many other applications. The system has been designed with advanced technology to provide high accuracy.

What is the difference between RTK and GPS?

There is a difference between RTK and GPS (Global Positioning System). GPS is used for navigation. It helps in finding an accurate location of the user.

On the other hand, RTK is used for surveying and measuring construction sites.

How can i choose between RTK and GPS?

There are many considerations to choose between RTK and GPS. To decide which technology is more suitable for a particular application, it is important to consider several factors, such as accuracy requirements, maintenance costs, project size and budget.

What is the difference between a static survey and a kinematic survey?

In general, two approaches are utilized in surveying. They are both kinematic and static in nature. During a static GPS surveying session, the receivers remain immobile on the Earth.

When real-time or near-real-time findings are required, kinematic GPS is used.

Is RTK necessary?

It is not necessary. It depends on the application of the survey.

What is RTK Tagging?

Real-time kinematic (RTK) tagging is an advanced GPS surveying technique that uses a differential correction signal with a carrier phase measurement made by an RTK base station to increase the accuracy of data.

GPS base stations equipped with a real-time kinematic receiver are commonly used for common survey applications.