The Complete Guide to Comparing GPS, GNSS, and RTK to Choose the Optimal Positioning System

Table of Contents

• Understanding GPS and GNSS: the basics

• Differences between standard satellite positioning and RTK, and accuracy differences

• The impact of positioning accuracy on practical work and selection criteria

• Infrastructure and correction information services required to implement RTK positioning

• Practical application examples of each positioning system and key points for on-site implementation

• Evolution and potential of positioning technologies leveraging smartphones

• Summary: choosing the optimal positioning system

Positioning technologies have become indispensable in many modern industries. Accurate location information is required across a variety of fields, such as operating heavy machinery on construction sites, autonomous driving in agriculture, and terrain surveying. However, terms like GPS, GNSS, and RTK are often used interchangeably, and many practitioners may find it difficult to understand their differences and the criteria for selecting among them. In this article, we clearly compare the characteristics, accuracy, and applications of these three positioning systems to help you choose the system that best suits your operations.

What are GPS and GNSS: Understanding the Basics

Before learning about positioning systems, it is important to understand the relationship between GPS and GNSS. GPS is a type of satellite positioning system developed and operated by the United States. GNSS, on the other hand, is a general term for satellite positioning systems and refers to multiple systems that include GPS.

GNSS includes satellite positioning systems operated by several countries and regions, such as the United States' GPS, Russia's system, the European Union's system, and China's system. By combining these multiple satellite systems, more satellites can be used, making more accurate and stable positioning possible.

GPS has long been widely used, but today, within the framework known as GNSS, systems that take advantage of multiple satellite constellations have become mainstream. This leads to improved positioning accuracy and increased reliability.

Differences between standard satellite positioning and RTK and their accuracy

There are two main methods for satellite-based positioning. One is standard satellite positioning, and the other is RTK positioning. The primary difference between them is the level of accuracy that can be achieved.

With standard satellite positioning, errors typically range from several meters (several ft) to several tens of meters (several tens of ft). This method is suitable for applications that require coarse location information, such as facility management and simple navigation. It receives signals from satellites and computes positions using simple calculations, so it is relatively straightforward and is used in many smartphones and car navigation systems.

RTK positioning, also called real-time kinematic positioning, is a method that receives correction information from a ground reference station in real time and uses that information to calculate position. Thanks to these corrections, positioning accuracy improves dramatically, achieving accuracies on the order of several centimeters (a few inches), and in some cases several millimeters (a few hundredths of an inch). This high precision is indispensable for tasks that require advanced accuracy, such as automatic steering of heavy machinery at construction sites, precision surveying, and autonomous operation in agriculture.

The reason RTK positioning can achieve high accuracy is that it uses a reference station located at a known position as a reference point. By calculating the measurement errors at the reference station and transmitting them to the moving receiver as correction information, it can almost eliminate error factors in the satellite signals (such as atmospheric effects and radio wave reflections).

The Impact of Positioning Accuracy on Practical Work and Selection Criteria

When selecting a positioning system for practical use, it is important to clearly define the accuracy required. Introducing an excessively high-precision system will, of course, increase costs. Conversely, choosing a system that does not meet the required accuracy will reduce work efficiency and increase rework in downstream processes.

In the construction industry, for general excavation work, standard satellite positioning may be sufficient. However, for projects such as asphalt paving on highways or earthworks that require precise terrain shaping, quality standards may not be met unless errors are at the level of a few millimeters (a few mm (0.04-0.20 in)). In such situations, the implementation of RTK positioning is essential.

The same applies in agriculture. For fertilizer spreading over large fields or pesticide spraying by drones, errors of a few meters (a few ft) may be within an acceptable range. However, when performing precise variable-rate fertilization to achieve optimal application rates according to soil fertility, more precise positioning is required. Furthermore, if the same locations are fertilized repeatedly over multiple years, introducing a high-precision positioning system is effective to prevent year-to-year positional shifts from accumulating.

The same is true in surveying work. In public surveys and cadastral (real estate) surveys, legal standards are set for the accuracy of deliverables, and these must be met. To satisfy these requirements, the use of RTK positioning is typically essential.

Therefore, when selecting a positioning system, it is important to first confirm the level of accuracy required for your company's operations and choose a system that can achieve that accuracy.

Infrastructure Development and Correction Information Services to Enable RTK Positioning

When implementing RTK positioning, simply buying a receiver is not enough. To achieve high-precision positioning, correction information is required. There are several ways to obtain this correction information.

One approach is to set up your own reference station and independently generate correction information. In this case, a large investment is required. There are many challenges, including selecting the site for the reference station, purchasing equipment, maintenance and management, and accurately determining position information. However, with an in-house reference station you have the advantage of being able to operate stably and continuously without relying on service providers. For operators of large construction sites or businesses that require continuous positioning over wide areas, this method can also be economically advantageous.

Another method is to use correction information services provided by telecommunications operators or surveying companies. Users receive correction information via communication networks (mobile phone networks or the Internet) and perform RTK positioning. This method has the advantage of low initial investment and ease of adoption because it can take advantage of existing communication infrastructure. It can be used on a nationwide scale and is not limited to specific regions, which is also a major benefit. However, challenges include ongoing service fees and the requirement for a communication environment.

Furthermore, the approach of using multiple satellite systems simultaneously is becoming more widespread. By receiving signals from multiple satellite systems at the same time and using them in calculations, more satellites can be leveraged, improving positioning accuracy particularly in environments where satellite signals are easily obstructed, such as urban areas and regions with dense tree cover.

When considering the introduction of RTK positioning, it is important to organize the advantages and disadvantages of these various methods for acquiring correction information and choose the method that best fits your company's business scale, operating region, budget, and other factors.

Practical Application Examples of Each Positioning System and Key Points for On-Site Implementation

Equally important to a theoretical understanding of positioning systems is how they are applied in real-world settings. The appropriate positioning system depends on the nature of the work.

The positioning system on a construction site is first used during the construction planning stage. It is employed for site surveying, confirming the locations of existing structures, and determining the construction area. At this stage, RTK positioning is generally adopted, because it serves as an important benchmark that determines the accuracy of subsequent work. If surveying accuracy is low, it will affect subsequent earthworks and the overall building construction.

Next, when introducing an automatic steering system for heavy machinery, high-precision positioning is indispensable. The conventional method, in which heavy equipment operators perform manual control, depends on experience and skill and cannot avoid human error. With an automatic steering system, RTK positioning enables precise position control to within several centimeters (a few in). This greatly improves grading accuracy and can simultaneously yield economic benefits such as reduced labor hours and lower fuel consumption.

In agriculture, the installation of positioning systems on tractors and drones is advancing. By receiving signals from satellites and determining the location of working machines in real time, more efficient operations are achieved. For example, drone-based pesticide spraying can prevent overlapping and missed areas, leading to reduced pesticide use and improved fertilization efficiency. When performing variable-rate fertilization, RTK positioning enables precise control of different application rates for each small plot within a field. This directly reduces fertilizer costs and environmental impact.

In surveying operations, combining modern surveying instruments such as T.L.S (terrestrial laser scanning) with RTK positioning enables the acquisition of high-precision three-dimensional terrain data. It is applied to a variety of uses, including inspection of public works, cadastral surveying, and damage assessment during disasters.

To successfully apply these in practice, advance preparation is important. It is desirable to deploy the system only after thoroughly checking the communication environment in the target area, planning the placement of reference stations, training operators, and so on.

The Evolution and Potential of Smartphone-based Positioning Technologies

In recent years, efforts to integrate high-precision positioning capabilities into mobile devices such as smartphones and tablets have been gaining momentum. Traditionally, high-precision positioning required dedicated surveying equipment, but advances in mobile device technology are beginning to change that.

The accuracy of standard GNSS receivers built into smartphones was traditionally on the order of several meters, but by simultaneously using multiple satellite systems and leveraging correction information, technologies have been developed that enable smartphones to achieve accuracy comparable to RTK positioning. This has given rise to new usage scenarios that do not require dedicated equipment.

For example, situations in which mobile devices play an active role at various sites—such as field surveys, basic construction management, property inspections, and disaster response—are increasing. Until now, tasks that required high-precision positioning relied on dedicated surveying equipment, but by attaching an attachment-style external GNSS module to a smartphone, lightweight, easy-to-carry, high-precision positioning has become achievable.

This approach can leverage the existing smartphone application ecosystem and makes data processing and management easy. It makes it possible to use a single device to handle multiple tasks that could not be achieved with conventional dedicated equipment.

Specialized solutions, such as iPhone-mounted GNSS high-precision positioning devices, have appeared on the market. These leverage the iPhone’s computational power and the convenience of a smartphone to achieve RTK-equivalent high-precision positioning. By attaching an external GNSS module to an iPhone, positioning solutions that integrate with existing iPhone applications can be built. They can be used for a variety of purposes—construction site management, agricultural work logging, and simple measurements in surveying work—making it possible to establish new workflows.

By adopting this technology, tasks that previously required multiple devices can be handled with a smartphone and a single external module, enabling both operational efficiency and cost reduction simultaneously. In particular, organizations that leverage existing iPhones can significantly improve positioning accuracy while keeping additional investments to a minimum.

Summary for Choosing the Optimal Positioning System

We have summarized the characteristics and uses of GPS, GNSS, and RTK. When selecting a positioning system, the most important thing is to first clarify the scope of work and the accuracy required. Based on that, you should comprehensively evaluate the methods for obtaining correction information, implementation costs, and operational effort, and select the optimal system.

If coarse location information is sufficient for an operation, standard satellite positioning is adequate. However, for operations that require high accuracy, introducing RTK positioning is essential. Recent advances in smartphone technology have made high-precision positioning—which previously required dedicated equipment—more accessible. Solutions such as iPhone-mounted GNSS high-precision positioning devices can be easily integrated into existing workflows and contribute greatly to operational efficiency.

By choosing the positioning solution best suited to your business operations, you can simultaneously achieve multiple benefits such as improved operational efficiency, enhanced quality, and cost reduction. Selecting the optimal positioning system is not merely a technical judgment but a strategic decision that takes the entire business into account.