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Robotic Total Station or RTK System? Which is Right For You?

As an engineer working in the field of geomatics, surveying, or construction, choosing the right equipment is crucial for accurate measurements, efficient workflow, and project success. Most surveyors have at some point used either a Total Stations or Real-Time Kinematic (RTK) Global Navigation Satellite System (GNSS). Each has its own set of advantages and disadvantages that engineers must consider when selecting the appropriate tool for their particular project. Let’s delve into the key points of comparison between Total Stations and RTK GNSS systems.

Total Stations

Total Station Advantages

Total Station Disadvantages

RTK GNSS Systems

RTK Systems Advantages

RTK Systems Disadvantages

Conclusions

FAQs

Total Stations

The total station is one of the most common survey instruments in the world and you can often spot one on the modern construction site. A total station is an optical instrument used in surveying and construction to measure angles, distances, and coordinates. It combines the functions of a theodolite and an electronic distance meter (EDM) into a single device. 

There are several different kinds of total stations, with the most common being the manual total station version. They are the least expensive, and require two operators, with at the total station, and one at the prism. Options like GeoMax’s Zoom10 are perfect for those with simple applications and will not be using the stations daily.

Next up in price is the robotic total station. A robotic total station allows a single user to place the prism, while the total station aims and measures autonomously. Popular examples include the Leica TS16Trimble S9 and GeoMax Zoom95 . 

Finally, the latest iteration on the total station is the multi-station. The multi-station incorporates a robotic total station and the scanning functionality of a LiDAR unit into one instrument. Due their recent introduction only a select number of companies currently offer options, with the Trimble SX10 and Leica Nova MS60 two of the more popular. 

Here are the advantages and disadvantages of total stations:

Total Station Advantages

1. High Accuracy: Total Stations offer very high angular and distance measurement accuracy, making them ideal for projects that require precision, such as land surveying and building construction. With the right instrument and operator, accuracy on single points can be brought below a centimeter. 

2. Suitable for Small Areas: In confined spaces or areas with obstacles, Total Stations can be more practical than GNSS systems, as they do not require a clear line of sight to satellites. This makes them ideal for work for the sky is obstructed, like that found under roofs, bridges and in between buildings. 

3. Data Collection Capabilities: Total Stations can collect a wide range of data, including angles, distances, elevations, and coordinates, which can be directly imported into CAD software for design and analysis. With the robotic and multi-station options, the environment can very quickly be digitized by a single user. 

4. No Signal Interference: Unlike GNSS systems, Total Stations are not affected by signal interference from nearby structures or vegetation, ensuring reliable measurements in challenging environments.

Total Station Disadvantages

1. Limited Range: Total Stations have one big limitation, and that is measurements must be within line of sight to the instrument in order to be recorded. In practice this means that in order to cover an entire site, the total station may need to be traversed. This requires a good understanding of survey practices, and a large amount of skill to do well. 

2. Time-Consuming: Setting up and aligning a Total Station for each measurement point can be time-consuming, especially in complex or rugged terrains. This may require the above-mentioned traversals, or performing an offset. The total station

3. Expertise Required: Compared to a GNSS system, a total station requires a lot more expertise. Users must understand fundamental surveying techniques to get the most out of their equipment and achieve their desired results. 

4. Calibration: Unlike GNSS systems, optical instruments require periodic calibrations. This is to ensure that the optical components have not drifted over time. On top of this, some work sites may require a calibration certificate in order to work. 

used surverying equipment

RTK GNSS

More and more, surveyors are adopting RTK GNSS systems into their workflows and businesses. With the advent of 7thgeneration RTK technology (Learn More Here), surveyors can reliably record positions under trees, near buildings and in other difficult environments. This has revolutionized the industry, with RTK GNSS seeing almost universal adoption. 

An RTK GNSS system relies on satellite signals to determine precise positions on the Earth’s surface. It typically consists of a rover receiver, a base station, and corrections transmitted in real-time. Some of the most popular receivers are the Trimble R12Leica GS18Sokkia GRx3/Topcon Hiper VR and Hemisphere S631. Here are the advantages and disadvantages of using an RTK GNSS system:

RTK GNSS Advantages

1. Large Coverage Area: RTK GNSS systems can cover large areas efficiently, making them suitable for projects such as highway construction, topographic mapping, and agriculture. Baselines of over 10 km can be achieved with UHF radio communication, and 20 km+ ranges can be achieved with solutions like StormCaster.

2. Rapid Data Collection: Once the system is set up and initialized, measurements can be taken quickly without the need for physical targets or line-of-sight constraints. Simply occupy the point, store the coordinates and move on. There is no need to worry about target acquisition. 

3. High Mobility: RTK GNSS rovers are portable and can easily move between measurement points, providing flexibility and speed in field operations. Coupled with the long range, large sites can quickly be covered with the need to haul equipment and perform traversals. 

4. 3D Positioning: GNSS systems can provide three-dimensional positioning data (latitude, longitude, and altitude), which is valuable for creating detailed digital terrain models (DTMs) and precise mapping. This data can then be easily transformed into your required coordinate system.

5. Calibration: As RTK measurements are a relative measurement, they never require calibration. This means that your unit never has to be sent for a calibration or service. 

RTK GNSS Disadvantages

1. Signal Interference: GNSS signals can be affected by obstructions such as buildings, trees, or atmospheric conditions, leading to potential inaccuracies in measurements. Although huge improvements have been seen with the latest equipment, you are still constrained by canopy conditions. For a test showing how GNSS performs under canopy see this video:

2. Accuracy: Compared to a total station, a GNSS receiver will not be able to achieve the same level of accuracy over short distances. Over short distances a total station is able to achieve accuracies in the range of singular millimetres. An RTK receiver at best will be able to achieve 8 mm of accuracy.

Conclusions

As technology continues to evolve, the potential for further enhancements in tilt functionality within RTK receivers is promising. Future iterations may focus on refining tilt capabilities, improving accuracy on extreme slopes, and expanding compatibility with other surveying tools and software.

The integration of tilt functionality into RTK receivers represents a significant leap forward in surveying technology. It addresses longstanding challenges in measuring points on slopes and uneven terrain, offering enhanced accuracy, efficiency, and safety. With its versatility and potential for further advancements, tilt-enabled RTK surveying is poised to redefine the landscape of modern surveying practices.

FAQs

1. What is the accuracy required for my projects?

   – Total stations typically offer higher accuracy compared to RTK systems, especially in situations where obstacles or interference might affect satellite signals. If your projects demand high precision, such as construction layout or boundary surveys, a total station might be more suitable.

   – RTK systems provide real-time centimeter-level accuracy when conditions are optimal, making them suitable for applications like topographic surveys, asset mapping, and agriculture where real-time data collection is essential.

2. What are the environmental conditions at my work sites?

   – Total stations rely on line-of-sight measurements and are generally unaffected by weather conditions such as rain, fog, or cloud cover. They can be used effectively in both indoor and outdoor settings, making them versatile in various environments.

   – RTK systems rely on GPS or GNSS signals and are susceptible to signal blockages caused by tall buildings, trees, or heavy vegetation. They may also experience accuracy degradation during periods of ionospheric disturbances or solar activity. Consider these factors when choosing between the two technologies.

3. What is the workflow and productivity requirement?

   – Total stations require setting up and sighting targets, which can take more time compared to RTK systems that provide real-time positioning. However, total stations excel in scenarios where precise measurements and angles are crucial.

   – RTK systems offer faster data collection and real-time feedback, enhancing productivity during field surveys, construction layout tasks, and precision agriculture operations.

4. What is the budget available for equipment and training?

   – Total stations generally have a higher upfront cost compared to RTK systems, including the instrument itself, prisms, tripods, and accessories. Additionally, training may be required to use the equipment effectively, especially for complex surveying tasks.

   – RTK systems are often more cost-effective in terms of initial investment and may require less training due to their user-friendly interfaces and real-time feedback capabilities.

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].

About the Author

Nolan has been working in the surveying field since 2017, starting as a part-time student at Bench-Mark while attending the University of Calgary. He now works in technical support and sales helping customers find the right product for them.

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