What is the Static Method? GNSS Survey Procedures, Time, and Accuracy Explained in 5 Minutes

Contents

‐ What the static method is ‐ Why the static method tends to be high-accuracy ‐ Basic procedures for the static method ‐ Typical time required for the static method ‐ How to interpret the accuracy of the static method ‐ Situations where the static method is suitable and not suitable ‐ Differences from RTK and the shortened static method ‐ Common points of failure on site ‐ Summary

What the static method is

In one sentence, the static method is "a way to obtain high-accuracy coordinates by fixing multiple receivers, observing simultaneously, and performing post-processing analysis." In the standards for public surveying, the static method is defined as placing GNSS survey instruments on multiple observation points, receiving satellite signals simultaneously, and deriving baseline vectors between observation points from baseline analysis. In other words, on site you first collect the data properly, and the final determination of results is done during the post-processing stage.

The important concept here is "relative positioning." In GNSS surveying, two or more receivers observe the same satellites simultaneously and use the differences in their observations to determine relative positional relationships. The Geospatial Information Authority of Japan (GSI) explains that by observing the same satellites at the same time, common errors such as satellite position errors and atmospheric delays are subtracted, allowing high-accuracy relative positional relationships to be obtained.

A characteristic of the static method is that, unlike conventional total stations, line-of-sight between observation points is not essential. In post-processed GNSS surveying, occlusion between observation points is less of a problem, making it useful for establishing control over wide areas or in areas where line-of-sight is difficult to obtain. However, conditions of the sky and surrounding environment—such as whether the sky is open, whether satellite geometry is biased, and whether there are nearby reflectors—remain important. e-education.psu.edu

In short, the static method is "a method to create reliable coordinates even if it takes time." It is not a method for producing points immediately but a method for building the foundation of coordinates for the entire site. Understanding it this way makes the differences from RTK and the shortened static method clearer.

Why the static method tends to be high-accuracy

The main reason the static method tends to be high-accuracy is that it can use the observation differences of multiple receivers that are looking at the same satellites at the same time. The GSI explains that in relative positioning, many errors such as satellite position errors and delays from the troposphere and ionosphere are subtracted, resulting in high-accuracy relative positional relationships between two points. Popular explanations also indicate that a rule of thumb for relative positioning is about 1 cm (0.4 in) over 10 km.

Another reason is that sufficient observation time can be secured. General guidance notes that static observations can last from 30 minutes to several hours or more, and the longer the observation time, the more reliable the analysis results tend to be. The required observation time is affected by baseline length: the longer the baseline, the more observation time is likely needed; conversely, the more satellites in view, the shorter the needed time tends to be.

Longer observations are also advantageous because they help mitigate multipath effects. Multipath is the phenomenon where signals reflected by trees, buildings, metal, vehicles, or water enter the receiver and destabilize GNSS coordinates. NGS guidelines state that multipath has periodicity and is easier to model with static, longer observations and post-processing, whereas it is harder to handle adequately in real-time observations that last only seconds to minutes.

However, "high precision" and "correct results" are not the same. Small scatter among measurements indicates precision, but whether the coordinates are truly correct must be judged including consistency with known points and reference coordinates. Even if the results look precise, if the placement of known points or handling of the reference frame is wrong, the entire result can be offset. e-education.psu.edu

In other words, the strengths of the static method are the combination of "ability to subtract common errors," "ability to take sufficient observation time," and "ease of quality checking in post-processing." Although it appears to be a simple task of leaving equipment standing on site, it is actually a well-reasoned scheme for high-accuracy positioning.

Basic procedures for the static method

Work for the static method begins with planning before going to the site. First decide which known points to use, which new points to connect, and which receivers to place in which sessions. The standards for public surveying require creating a session plan for the static method and, except when using only electronic reference stations as known points, arranging known and new points so that the polygonal routes that connect them form closed loops or so that redundant observations allow checking. In other words, it is important to build a network that can be checked later, not just to observe.

Next is selection of observation points. Although the static method tolerates occlusion, you should avoid locations with poor sky view or near buildings, trees, metal fences, parked vehicles, or water surfaces. The basics are to avoid biased satellite geometry, pay attention to the minimum elevation mask setting, and choose places with few reflectors. If the observation point itself is unstable or multipath is strong nearby, even long observations may yield poor-quality data. e-education.psu.edu

On site, correctly mount the receiver over the point, perform centering and leveling carefully, and measure the antenna height accurately. The standards for public surveying require that antenna height be measured to the millimeter (mm) and that, for the static and shortened static methods, the standard is to measure vertically from the top of the mark to the bottom of the antenna. The GSI also advises that when performing baseline analysis between different antenna models, applying PCV corrections and unifying antenna height measurement helps improve vertical accuracy.

During observation, begin data collection simultaneously at multiple points and continue stable reception until the scheduled time ends. For successful static GNSS, it is important that simultaneous observations be established at both ends of the baseline; if one side starts late or ends early, usable data may be insufficient. On site, always record observation times, equipment, antenna heights, and surrounding conditions so that analysis and rechecks can be performed later. e-education.psu.edu

After observation, bring the receiver data back to the office and perform baseline analysis and network adjustment. Only here are the coordinates of each point evaluated: you judge the results by checking redundant observations and closures, residuals, and quality indicators. Although it may seem roundabout because you do not get numbers on site, this ability to "thoroughly check later" is what underpins the reliability of the static method.

A common oversight by beginners is thinking that the static method ends once the receiver is set up. Observation planning, setup accuracy, antenna height, session overlap, and analysis conditions form a single workflow; if any part is handled carelessly, the reliability of long-duration observations can be compromised. Conversely, if you control this workflow, the static method becomes a very reproducible technique. e-education.psu.edu

Typical time required for the static method

You cannot universally decide "how many minutes to stop" for the static method. However, there are easy-to-understand reference values in Japan's public surveying standards. The procedural standards state that for 1st–3rd class control point surveys, the static method standard is at least 120 minutes for observation distances of 10 km or more and at least 60 minutes for distances less than 10 km, and that the shortened static method standard is at least 20 minutes for 3rd–4th class control point surveys.

General GNSS operation guidance notes that static observations can range from 30 minutes to several hours or more, and the required time depends on baseline length, the number of satellites in view, the desired accuracy, and the surrounding environment. The practical rule that longer baselines generally require longer observation times and that more satellites in view generally reduce required time is very important in practice. In other words, rather than memorizing whether it should be 60 minutes or 120 minutes, it's more useful on site to understand "shorter for short baselines/good sky/sufficient satellites, longer for long baselines/poor sky/high accuracy requirements."

Also, on-site observation time is not the whole story for total work time. Travel, setup, centering, antenna height measurement, observation log recording, teardown, and office data processing and analysis follow. Unlike RTK, which feels like finishing the job on the spot, the static method must be thought of as "observation and analysis as a set." It is said to take longer largely because of this operational difference that includes post-processing.

Therefore, when beginners estimate time, it is realistic to consider not only "observation time" but also "setup and follow-up time." Cutting observation time too much to finish quickly can lead to re-observation later and ultimately increase total workload.

How to interpret the accuracy of the static method

When considering the accuracy of the static method, first separate "what accuracy you mean." The GSI's explanation of relative positioning indicates that you can obtain high-accuracy relative positional relationships between two points, and static GNSS is a representative use of that. NGS also positions static GNSS as relative positioning by post-processing and states it is the GNSS method that yields the highest accuracy and reliability.

However, what is needed on site is not just apparent precision. Even if coordinate scatter looks small, if the known point coordinates are not trustworthy, the overall positions will not be correct. Precision and accuracy (trueness) are different; only when consistency with known points, coordinate systems, vertical datums, and reference surfaces is confirmed does the result become "usable." One reason static methods are emphasized in control surveys is that they allow careful accumulation of these foundational coordinate consistencies. e-education.psu.edu

Significant error sources include incorrect antenna height measurements, centering errors, multipath, biased satellite geometry, occlusion, observation times that are too short, and overlooking bad data during analysis. In particular, antenna height is pointed out by NGS as one of the most frequent mistakes in GNSS surveying and can easily contaminate vertical results. The GSI also advises that PCV correction and unified antenna height measurement are important for improving vertical accuracy. e-education.psu.edu

In practical judgment of accuracy, you should not rely solely on software numbers: confirm that redundant observations agree, closures are reasonable, residuals are not biased, and observation logs show no anomalies. The static method does not produce accuracy simply because equipment was left standing; accuracy comes from "taking good observations, performing good analysis, and conducting good checks."

Situations where the static method is suitable and not suitable

The static method is well suited to establishing control points and maintaining control networks. When you want to build a solid coordinate foundation before construction, reliably connect new points from known points, or obtain trustworthy results even for relatively long baselines, the static method offers great value. Because quality can be checked in post-processing, it is especially appropriate for tasks that emphasize the basis for coordinates. e-education.psu.edu

Another advantage is that it is usable in areas where line-of-sight between observation points is difficult. Since post-processed static GNSS is not fundamentally hindered by occlusion between observation points, it can be planned even in large or undulating sites. Also, because it does not require communication of correction information on site, it is a good choice when you do not want to rely on real-time communication environments. e-education.psu.edu

On the other hand, the static method is not suitable when you need to produce many points on site quickly. For tasks such as staking out, immediate positioning, or on-the-spot verification of as-built form, RTK or network RTK methods are often easier to operate. The GSI also explains that RTK systems can perform real-time processing to achieve position determination at the centimeter level.

Moreover, in urban areas with narrow sky views, densely treed sites, or places with many reflectors, the static method is not a panacea. Although longer observations can mitigate issues to some extent, a bad observation environment cannot be turned into a good one by observation time alone. In such places, it may be better to shift the observation point and perform offset observations.

Differences from RTK and the shortened static method

The clearest way to describe the difference between the static method and RTK is in "when results are produced" and "where you place your emphasis on reliability." The static method collects data on site and finalizes results through baseline analysis later. RTK uses information from a base station while the rover performs immediate processing to determine position on site. RTK is fast; the static method is deliberate and certain.

The shortened static method is easiest to understand as an approach intermediate between the two. In the standards for public surveying, the shortened static method is described as a static method variant that shortens observation time by creating many different satellite combinations in baseline analysis, with a standard observation time of at least 20 minutes. In other words, it retains the static method’s approach while shortening on-site time.

However, the shortened static method is not simply a "short static method." If observation conditions, equipment performance, placement of known points, baseline length, or satellite environment are poor, shortening time makes quality control more stringent. Being able to shorten time and producing the same accuracy in any field are different things. The shorter the observation time, the more the influence of site conditions will show up in the results.

As a practical rule of thumb: use the static method for establishing control points and foundational coordinates; use the shortened static method when you need a larger number of points and still want post-processed quality; and use RTK when immediacy is the top priority. The important thing is not to choose by the method name but to decide first whether you need immediacy, reliability, or foundational coordinate control.

Common points of failure on site

A frequent failure point in the static method is handling simultaneous observations. In static GNSS, it is critical that common satellite observations exist at both ends of a baseline; if one side starts late or is withdrawn earlier than planned, usable data volume can become insufficient. On sites with multiple receivers, strictly managing start and end times is safer. e-education.psu.edu

Another common mistake is antenna height errors. In GNSS surveying, mistakes measuring antenna height are very common, and even excellent observations can have their vertical results spoiled by such errors. Public surveying standards require millimeter-level measurement, and the GSI emphasizes unifying antenna bottom height measurement and PCV correction. Developing a habit of double-checking records and data entry rather than measuring once and forgetting is important. e-education.psu.edu

Third is underestimating multipath and occlusion. Trees, buildings, metal fences, water surfaces, and nearby parked vehicles are error sources even for static observations. Although long observations and post-processing make these easier to handle to some extent, you should not assume a bad observation environment is acceptable. Avoid reflectors when choosing observation points, and if unavoidable, plan for offset observations.

Fourth is blindly trusting software outputs. Data defects and cycle slips can be hard to detect on site. Educational materials on static GNSS stress the importance of daily quality checks and being able to pick up bad vectors or unhealthy data the next day. Redundant observations, closures, log reviews, and decisions on re-observation are all part of complete quality control for the static method. e-education.psu.edu

In the end, the key to stable results with the static method is not a special trick. Choose good points, set up carefully, allow sufficient time, treat antenna height accurately, and always check after analysis. The basics directly translate into differences in results in the world of the static method. e-education.psu.edu

Summary

The static method is a fundamental GNSS surveying technique in which multiple receivers are fixed and observed simultaneously, and high-accuracy coordinates are obtained by post-processed baseline analysis. It lacks real-time immediacy but has major strengths in reducing common errors through relative positioning, allowing sufficient observation time, and enabling quality checks in post-processing, all of which make it likely to yield highly reliable results. Recommended observation times vary with baseline length and class, and in practice may be 60 minutes, 120 minutes, or longer; more important than memorizing numbers is understanding why the time is necessary.

If you are starting high-accuracy positioning, the static method is an excellent introduction to the mindset of "creating reliable coordinates." In daily fieldwork, many will also want the convenience of using a smartphone for high-accuracy positioning. For those readers, options such as LRTK, an iPhone-mounted GNSS high-precision positioning device, naturally provide a way to begin high-accuracy positioning centered on a smartphone. The foundational understanding of coordinates cultivated by the static method and agile high-accuracy positioning with a smartphone are not opposed; when used appropriately on site, they are complementary.