Surveying is an essential process and is often the first step in any new project. Whether it be in construction to engineering projects to agriculture and environmental science. The accuracy and precision of survey equipment directly impact the quality of data collected, which in turn influences decision-making and project outcomes. In this article, we are going to take a look at the various types of survey equipment, including those offering RTK level accuracy, decimeter (L-Band) accuracy, sub-meter (SBAS) accuracy, and consumer-level accuracy. We will take a look at the differences between these accuracy levels, the technology behind them, and the contexts in which each type is most suitable. By understanding these aspects, surveyors can make informed choices about the equipment that best meets their needs.
Introduction to Survey Accuracies
Comparison and Decision Making
Accuracy in surveying refers to how close a measured value is to the true value or a standard reference. The level of accuracy required varies depending on the project’s needs, ranging from high-precision applications like land surveying and construction to lower-precision needs like recreational mapping or agricultural field planning. Here are the four main categories of survey equipment based on accuracy:
RTK (Real-Time Kinematic) Level Accuracy
Decimeter (L-Band) Accuracy
Sub-Meter (SBAS) Accuracy
Consumer Level Accuracy
Each category utilizes different technologies and methodologies to achieve its accuracy, influencing its cost, complexity, and suitability for various applications. For an idea of what this looks like for you in the field, check out this video below.
In terms of accuracy, RTK is the highest achievable level in real time, satellite-based positioning. With accuracies often under an inch achievable. This level of accuracy is critical for applications where minute deviations can have significant consequences, such as in construction, cadastral surveys, and precision farming.
Technology Behind RTK
RTK technology involves the use of GNSS (Global Navigation Satellite System) receivers in combination with a network of base stations and rovers. The base station remains fixed at a known location, while the rover moves and collects data. The base station provides real-time correction data to the rover, allowing it to correct any errors caused by atmospheric disturbances, satellite orbits, and clock errors. This real-time correction process is what enables RTK systems to achieve such high levels of accuracy.
A typical base and rover RTK setup. The particular system in this photo is the Hemisphere S631, a 7th generation RTK receiver.
RTK Applications
RTK systems are used in:
Advantages and Disadvantages
Advantages:
Disadvantages:
An RTK system being set up for use in the field on a construction site. The versatility of RTK is making it one of the most common tools on the modern construction site.
Decimeter Accuracy typically refers to positioning systems that can achieve precision within 10-20 centimeters. This level of accuracy is suitable for applications that require higher precision than consumer-grade devices but do not necessitate the extreme precision of RTK systems.
Technology Behind L-Band
Decimeter accuracy is often achieved through L-Band satellite services, which provide correction signals to GNSS receivers. These correction signals help to minimize errors, improving the overall accuracy of the positioning data. L-Band services use geostationary satellites to broadcast corrections over a wide area, making them more flexible and easier to use compared to RTK systems. Often, private companies will deploy these systems to cover areas where public SBAS (Satellite Based Augmentation System) systems are lacking coverage. This includes areas like the ocean, and far north.
Current deployment of SBAS systems around the world. Private L-Band services like Hemisphere’s Atlas service are designed to fill in areas that would otherwise be left uncovered by public SBAS systems. (Image from ESA Website: https://www.esa.int/ESA_Multimedia/Images/2023/09/SBAS_coverage)
Applications of Decimeter Accuracy
L-Band systems are commonly used in:
Advantages and Disadvantages
Advantages:
Disadvantages:
Sub-Meter accuracy is defined as positioning that is accurate to within one meter. Typically, in areas with SBAS coverage, positional accuracy is within 3 feet, or 0.5 m. This level of accuracy is achieved using SBAS (Satellite-Based Augmentation Systems), which enhance the performance of standard GNSS.
Technology Behind SBAS
SBAS systems, such as WAAS (Wide Area Augmentation System) in North America, EGNOS (European Geostationary Navigation Overlay Service) in Europe, and MSAS (Multi-functional Satellite Augmentation System) in Japan, provide correction signals to GNSS receivers. These systems use a network of ground reference stations that monitor GNSS signals and a set of geostationary satellites that broadcast correction data. The corrections improve the accuracy and reliability of GNSS positioning.
A GIS tablet being used to record the position and condition of a fire hydrant. Using FieldGenius, it is very easy to record the position and all relevant information on the condition of an asset.
Applications of Sub-Meter Accuracy
Sub-meter accuracy is suitable for:
Advantages and Disadvantages
Advantages:
Disadvantages:
Devices that can provide positioning accuracy within a few meters, are commonly categorized under consumer devices and are not recommended for professionals. These devices are widely available and used in everyday applications where high precision is not critical.
Technology Behind Consumer Devices
Consumer-grade GNSS devices, such as those found in smartphones, car navigation systems, and handheld GPS units, rely on standard GNSS signals without any augmentation or correction. The accuracy of these devices can vary depending on the quality of the GNSS receiver, environmental conditions, and satellite geometry.
Applications of Consumer Accuracy
Consumer-level accuracy is adequate for:
Car navigation systems often use basic GNSS modules capable of giving a position with an accuracy of 1-5 m, more than sufficient for driving on the road.
Advantages and Disadvantages
Advantages:
Disadvantages:
Choosing the right survey equipment depends on several factors, including the required accuracy, budget, and specific application needs. Here’s a comparative summary to help guide the decision-making process:
Accuracy Requirements
Budget Considerations
RTK Systems: Most expensive due to high precision and complex setup. It is highly recommended talking to a surveying equipment dealer to find the right system to meet your specific needs.
L-Band Systems: Moderately expensive with subscription fees for correction services. Talking to a company that specializes in these systems is often a good idea to ensure that you get the subscription length and accuracy that meets your needs.
SBAS Systems: Generally cost-effective as they use free correction services. Simple units like Juniper’s Geode can be purchased off the shelf and easily integrated with many different types of software.
Consumer Devices: Least expensive and widely available. Systems can be bought online or in any electronics store to meet your needs.
Selecting the right survey equipment is crucial for ensuring the accuracy and reliability of the data collected. RTK level accuracy provides the highest precision, suitable for critical applications but at a higher cost and complexity. Decimeter accuracy via L-Band services offers a middle ground with good accuracy and easier setup, though still at a higher cost than basic systems. Sub-meter accuracy from SBAS systems is cost-effective and sufficient for many applications in GIS and environmental monitoring. Finally, consumer-level devices offer the lowest cost and ease of use, suitable for recreational activities and basic mapping.
By understanding the different levels of accuracy, the underlying technologies, and the specific needs of their projects, surveyors can make informed decisions about the most appropriate equipment to use. This ensures that the data collected is both accurate and cost-effective, ultimately leading to better project outcomes and more efficient workflows.
RTK Level Accuracy:
– Achieves centimeter-level precision.
– Uses a network of GNSS receivers, base stations, and real-time corrections.
– Suitable for high-precision applications such as construction, cadastral surveys, and precision farming.
– Higher cost and more complex setup.
Consumer Level Accuracy:
– Provides accuracy within a few meters.
– Utilizes standard GNSS signals without additional corrections.
– Suitable for recreational activities, vehicle navigation, and basic mapping.
– Low cost and easy to use.
Decimeter (L-Band) accuracy devices offer a balance between precision and ease of use. They provide accuracy within 10-20 centimeters, making them suitable for applications like agricultural machinery guidance and marine navigation, where RTK’s centimeter-level precision is not necessary. L-Band systems are less expensive and easier to set up than RTK systems, which require a network of base stations and more complex maintenance.
Sub-Meter Accuracy with SBAS:
– Achieved through Satellite-Based Augmentation Systems (SBAS) like WAAS, EGNOS, and MSAS.
– Use ground reference stations and geostationary satellites to broadcast correction signals.
– Improve GNSS signal accuracy to within one meter.
Advantages:
– Cost-effective, often with no subscription fees.
– Easy to use and widely accessible.
– Suitable for GIS, environmental monitoring, and asset management.
Consumer-level survey equipment, such as those found in smartphones and handheld GPS units, is sufficient for scenarios where high precision is not critical. These include:
– Recreational activities like hiking and geocaching.
– Vehicle navigation for turn-by-turn directions and route planning.
– Basic mapping tasks for non-critical applications.
RTK Systems:
– Highest cost due to the need for multiple GNSS receivers, base stations, and real-time correction services.
– Suitable for applications requiring the highest precision.
L-Band Systems:
– Moderately expensive, often requiring subscription fees for correction services.
– Provide good accuracy with easier setup compared to RTK.
SBAS Systems:
– Generally cost-effective, with no additional subscription fees as they use free correction services.
– Provide a balance of cost and accuracy.
Consumer Devices:
– Lowest cost and widely available.
– Suitable for applications where a few meters of accuracy are acceptable.
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 +1 (888) 286-3204 or email us at [email protected]
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