How to Use CLAS Positioning and the Procedure | Configuration Points to Avoid Confusion On Site

CLAS positioning is a positioning method that is highly valuable for field personnel who want to handle high-precision location information on site. By utilizing correction information broadcast from satellites, it can aim for higher accuracy than standalone positioning, so it is attracting attention for situations where improving efficiency and reducing labor in positioning tasks is considered.

On the other hand, even if people know the term CLAS, it is not uncommon that they are unsure how to actually use it, what procedure to follow to avoid getting lost in settings, or what to check on site. Especially for those handling high-precision positioning for the first time, it can be difficult to understand whether communication is needed, whether it can be used stably at any time, and what kinds of locations it is suitable for.

This article organizes, from a practical perspective, the basics of CLAS positioning, concrete usage on site, preparations before work, configuration points that tend to cause confusion, and how to review settings when accuracy is unstable. It is compiled to be useful both for those considering introduction and for those who have already started using it but whose operations are not stable.

Table of Contents

• What CLAS positioning is

• Tasks suitable and unsuitable for CLAS positioning

• What to prepare before entering the site

• Key points to check in basic CLAS positioning settings

• How to use CLAS positioning and the work procedure

• Configuration points that tend to cause confusion on site

• How to review CLAS positioning when accuracy is unstable

• Operational concepts to make CLAS positioning useful in practice

• Summary | Standardizing procedures is important to avoid confusion

What CLAS positioning is

CLAS positioning is a method that uses correction information broadcast from satellites to aim for higher accuracy than ordinary satellite positioning. There are several concepts for high-precision positioning commonly used on site, but CLAS is characterized by differences in how correction information is received and operated compared to typical communication-based corrections. For that reason, it tends to attract interest in situations where dependence on communication environments should be minimized or where mobility is emphasized.

However, if you understand CLAS as a万能 positioning method just by the name, gaps will appear after introduction. High-precision positioning is influenced by conditions such as whether the sky is open, whether satellite reception is stable, and whether the surroundings are less prone to obstruction or reflection—regardless of the method. In other words, using CLAS does not automatically lead to high accuracy at all times; it is important to operate it with appropriate settings and procedures after understanding the prerequisites for use.

What practitioners should understand is that CLAS is not simply an item to select in a device menu; it tends to perform well only when site conditions, equipment status, satellite reception environment, and work procedures come together. Deeply learning the differences between positioning methods is also important, but for field personnel it is more useful to first grasp in which environments CLAS is easy to use and where caution is needed.

Also, when using CLAS positioning, it is important not to accept positioning results uncritically but to check consistency with known points or reference points as needed. Relying only on the word “high precision” makes it easy to overlook small discrepancies that occur on site. In practice, you need to check not only displayed numbers but also whether the results make sense compared with past data, drawings, and the positions of existing control points.

Tasks suitable and unsuitable for CLAS positioning

CLAS positioning is well suited for tasks that require quickly grasping a relatively wide area on site or obtaining reference positions with reasonably high accuracy. For example, it is a good match for situations where mobility and a certain level of accuracy are both required, such as site condition surveys, geotagging photos, rough pre-construction assessments, on-site verification of temporary plans, simple as-built checks, and management of material placement or temporary structures.

In particular, when you want to acquire multiple points in a short time while walking the site, high usability is a major advantage. Traditional positioning work can require time for equipment setup and installation, but with equipment configurations that support CLAS, you can often move more nimbly. On sites with limited personnel or with many points to check, this difference directly affects overall work efficiency.

On the other hand, CLAS is not always optimal. In places where the sky is largely obstructed—such as dense tree stands, near mountain edges, directly below slopes, or in narrow areas surrounded by structures—satellite reception tends to be unstable and expected accuracy may not be achieved. Also, for highly precise control tasks that cannot tolerate even slight errors, or for coordinate determinations that greatly affect downstream processes, it may be necessary to combine other positioning methods or verification steps depending on the work objectives.

What is important here is not to decide suitability based only on the method name. You need to assess comprehensively factors such as how open the sky is at the site, the time of work, required accuracy, number of workers, quality required by downstream processes, and the allowable range for remeasurement. CLAS is a convenient option, but rather than having excessive expectations about site conditions, the quickest path to success is to use it reliably for appropriate applications.

As a practitioner, it is helpful to first categorize your company’s tasks into those suitable for rough overview, routine checks, and those requiring strict control. Then organize where CLAS will be most effective, which will make judgments after introduction less confusing.

What to prepare before entering the site

To use CLAS positioning stably on site, it is often too late to start thinking about settings after arriving. For high-precision positioning, results are often determined more by pre-work preparation than by on-site operations. Especially for sites where it will be used for the first time, standardizing pre-work checks is important.

The first thing to confirm is whether the equipment you will use supports CLAS. Don’t judge by name alone; you need to confirm which satellite signals and correction information can be received, the conditions for using the corrections, and the compatibility with the applications and terminals you will use. High-precision positioning equipment results can change not only with the main unit’s performance but also with terminal settings and connection status. Don’t assume the equipment will work just because it has been procured—test it in a fixed or open location before taking it to the field to be safe.

Another important point is to standardize how coordinates are handled within your company. Even if you can acquire positions on site, the coordinates will be of limited use in practice if they don’t match drawings or existing data. Decide in advance not only on horizontal coordinates but also on vertical datum, coordinate systems, output formats, and naming conventions for records to prevent confusion downstream. Especially when multiple people will operate the equipment, standardize initial settings to avoid situations where each person has different configurations.

Additionally, understanding the site environment is indispensable. Since satellite positioning is affected by how the sky is visible, check in advance whether there are tall buildings nearby, whether trees are dense, or whether the planned work location is in a valley. This makes on-the-day decisions easier. This perspective is also important to distinguish whether failures on site are due to equipment issues or environmental problems.

Also check basic items that are easy to overlook, such as battery levels, terminal storage capacity, log save locations, time settings, and permissions for using location information. Problems in high-precision positioning can seem to stem from advanced causes but often originate from basic issues like lack of power, connection failures, or incorrect save settings. To avoid stopping field work, don’t neglect these basic checks.

Key points to check in basic CLAS positioning settings

Settings are where users are most likely to get lost when using CLAS positioning. Even if there are several items displayed on a screen, choosing them without understanding the meaning can lead to problems such as positioning not starting, accuracy not stabilizing, or records being of poor quality despite appearing to be measured. Here are the setting points to pay particular attention to on site.

First, be clear about the selection of positioning mode. High-precision positioning equipment may offer multiple modes, and if you select a different method when you intend to use CLAS, the device will not behave as expected. Conversely, even if CLAS is selected, it may not be stable if reception conditions are not adequate. The important point is not to stop at selecting the mode name but to confirm on the display whether correction information is actually being received and whether the solution has stabilized.

Next, check satellite reception status. A larger number of received satellites does not necessarily guarantee good results, but stable positioning requires adequate reception conditions. Don’t assume it is fine simply because the current position is displayed; observe changes in positioning status and fluctuations in accuracy indicators to judge whether it is acceptable to start recording. Especially immediately after starting positioning, conditions may not yet be stable, so avoid rushing to collect points.

Vertical settings and coordinate system settings are also crucial in practice. Even if the horizontal position appears correct, a different vertical datum can lead to large discrepancies when comparing with drawings or design data later. Since horizontal matches can be visually convincing, this issue is easy to miss and later cause problems. Therefore, don’t treat configuration as a one-time task; make it a habit to check settings both before and after data output.

Settings related to timing of recording should not be overlooked. With settings that allow immediate saving, you may accidentally record while positioning is still fluctuating. Conversely, incorporating concepts like averaging or stability criteria can improve record quality. Prioritizing speed to take points one after another can leave you with data that is difficult to use later.

In practice, it is more important to understand which settings affect accuracy and which affect record quality than to memorize specific values. With that understanding, you can quickly judge which items to check as site conditions change.

How to use CLAS positioning and the work procedure

When using CLAS positioning on site, viewing the work as a sequence reduces failures. Instead of simply starting the device and taking points, proceed through the flow of pre-start checks, initial stabilization, trial measurement, main measurement, record verification, and post-processing checks.

The first step is to check the environment upon arrival. Actually look at how open the sky is and confirm whether the planned measurement position is suitable for satellite reception. Even if pre-surveys suggest no problems, temporary structures, vehicles, materials, or overhanging trees may change conditions on site. At this stage, moving the measurement position slightly can often greatly improve reception.

Next, power up the equipment and check satellite reception and correction information status. The important point here is not to enter the main measurement immediately after startup. In high-precision positioning, waiting for reception to stabilize can significantly affect results. Although you may be in a hurry on site, allowing a few minutes at the start can prevent the need for re-measurements later. Observe the displayed positioning status, accuracy trends, and correction reception state and wait until you judge the system to be stable.

After that, rather than immediately collecting primary data, perform a trial measurement at a known location or a visually easy-to-verify spot. For example, check near a point whose coordinates are already known, a previously measured position, or a readily reproducible landmark to catch configuration mismatches or recording method errors. Skipping the trial measurement risks proceeding with incorrect settings for the whole day’s work.

In the main measurement, stabilize the device attitude at each point and record while observing fluctuations in positioning status. Values may not settle immediately after moving or when people are moving around, so pause briefly before recording. Checking reproducibility by acquiring the same point repeatedly makes it easier to judge whether positioning is truly stable. Don’t be reassured by a single acquisition—apply stricter confirmation to important points.

After acquisition, perform a simple on-site check. Verify point names, coordinate order, relationships with surroundings, and whether values deviate from expected ranges to reduce the risk of having to return to the site. Discovering recording mistakes after leaving the site can necessitate revisit. The practical value of high-precision positioning comes not only from acquisition but from inspecting the acquired results on site.

Finally, when back at the office, check the data again for coordinate system, recording date and time, point names, and consistency before and after. Even when you think you took data correctly on site, output settings or data conversion can introduce unintended shifts. Therefore, consider the work procedure as a single operation that includes data verification, not just on-site work.

Configuration points that tend to cause confusion on site

In CLAS positioning operations, common uncertainties include when it is acceptable to take a point, how long to wait before judging the data as stable, and whether to continue or stop operations under poor site conditions. These are aspects not easily understood by device manuals and often cause practical dilemmas.

A common source of confusion is how to handle the period immediately after positioning starts. Even if a position is displayed on the screen, it does not necessarily mean it is of immediately usable quality. Rather than recording just because it is shown, judge based on whether fluctuation ranges are small and whether the positioning status has settled. Inexperienced field staff tend to think work can begin as soon as the device responds, but rushing here increases re-measurements.

Next is the dilemma of whether to continue working in locations with partial sky obstruction. Ideal sites are not always available. However, there is a difference between slightly poor conditions and conditions that significantly affect accuracy. The important practice is to perform multiple checks at the same point over time in obstructed locations and evaluate reproducibility. Adopting a result based on a single measurement in poor conditions may appear plausible but later reveal discrepancies.

Height handling is another area of uncertainty. On site, attention tends to focus on horizontal position, while vertical datum checks are often postponed. However, height consistency is crucial for design verification, volume calculations, and cross-section checks. Horizontal agreement alone may be insufficient for practical use, so decide in advance which vertical datum to use and how to align it with in-house drawings and existing data.

Also, naming conventions and save rules for measurement points should not be neglected. High-precision positioning is meaningful only when records remain usable later. If point names are ambiguous or record formats differ across operators, collected data becomes hard to use. While field workers tend to concentrate on measurement itself, the operational rules for post-measurement data use are where real differences appear in practice.

In short, to avoid confusion in CLAS positioning, it is more important to have judgment criteria than to memorize settings. Share within the team what constitutes a stable state, what conditions are acceptable for recording, and how to increase checks under poor conditions to reduce variability between operators.

How to review CLAS positioning when accuracy is unstable

If you find that CLAS positioning does not stabilize to the expected level, results fluctuate at the same location, or values vary over time, it is important to review basic conditions in order before suspecting the equipment itself. Troubles in high-precision positioning are often caused by multiple factors, and you can misidentify the cause if you do not isolate them one by one.

The first thing to check is the site environment. Satellite positioning is strongly affected by sky visibility, so it tends to be unstable near building edges, close to trees, below slopes, or near vehicles and heavy machinery. Reflections near metal surfaces or structures are also non-negligible. In such places, environmental conditions may be too severe regardless of the device’s capabilities, and moving the measurement location slightly can lead to improvement. Because results can change with just a few steps, start by reviewing the measurement location.

Next, review the waiting time from starting positioning to recording. In the pursuit of work efficiency, it is not uncommon for recordings to be made without waiting for stabilization. This is especially true when repeatedly moving and collecting points. Even when values appear steady, the internal state may still be stabilizing, so for important points, observe the state a bit longer and re-acquire as needed.

Also review settings. If any of positioning mode, coordinate system, vertical datum, recording settings, or terminal connection state is incorrect, reliability falls. When equipment is shared among multiple people, previous settings may remain. When things go wrong, one may be tempted to consider advanced causes, but often the root is a setting handover mistake.

Comparing with known points is also effective. If you only have a vague sense that things are unstable, you cannot judge properly—measure repeatedly at a known location to see how much it deviates, whether there is reproducibility, and whether tendencies change over time. This comparison helps determine whether fluctuations are incidental or persistent. Evaluate by comparison rather than by feel.

If instability persists, it may be that the environment for using CLAS is simply unsuitable for that site. High-precision positioning is not omnipotent. Important here is not to force acceptance of results on site but to change the work method according to conditions. In harsh locations, consider supplementing by changing locations, rechecking in downstream processes, or reinforcing with other control points. When accuracy is unstable, the priority on site is to protect quality, not to stubbornly continue using the system.

Operational concepts to make CLAS positioning useful in practice

To make CLAS positioning effective in practice, incorporate it into company operations rather than using it as a one-off. No matter how good a positioning method is, quality will not be stable if operations rely on the intuition of individual operators. If usage and checks differ by site and by person, even high-precision positioning cannot be fully utilized.

First, standardize pre-work checks. If you can follow the same sequence each time—device condition checks, settings checks, coordinate system confirmation, site condition review, trial measurement, and re-measurement of important points—you will reduce trouble. People tend to omit checks when they become used to a process, but in high-precision positioning such omissions directly reduce data quality. Established standard procedures help new personnel perform at the same quality level.

Next, clarify usage distinctions by application. Not all tasks require the same accuracy. The depth of checks should vary for rough overviews, tasks where you want to geotag photos or records, and tasks that need near-construction-level control. After introducing CLAS, don’t measure everything the same way; decide in advance how much verification is required by application to balance efficiency and quality.

Also consider how you will use the acquired data. Positioning does not end with taking points. You need to record with downstream uses in mind—updating drawings, site condition verification, sharing with stakeholders, creating comparison materials, and ensuring consistency with future re-measurements. Seemingly minor operational details such as point naming, folder structure, linking with photos, and how to record measurement times have practical impact.

Moreover, share not only success stories but also failure cases in the field. Accumulate as a team which conditions were unstable, which setting mistakes occurred often, and where re-measurements happened. This refines CLAS usage to fit real field conditions. Practical judgment criteria, which cannot be covered by device manuals alone, will develop through this process.

When used correctly, CLAS positioning can significantly improve field productivity. However, its value is determined by operational design rather than the method name. Whether you can create a state where anyone can work without confusion greatly affects the effect of introduction.

Summary | Standardizing procedures is important to avoid confusion

What matters most in using CLAS positioning is not knowing the method name but having procedures on site that prevent hesitation. Which device to use and what settings are available are of course important, but in practice, even more critical is the order in which you check things, the state in which you record, and how you verify results—these determine quality.

CLAS positioning tends to be powerful in places where an open sky is easy to secure, for mobile site verification, simple position acquisition, and routine positioning tasks. Conversely, in areas with strong obstructions or where strict consistency is required, careful judgment and additional checks are necessary. In other words, it is important to understand not whether it can or cannot be used, but where and how its strengths manifest.

To avoid failures on site, always follow the flow of pre-work preparation, settings confirmation, initial stabilization, trial measurement, main measurement, and record verification. Particularly, do not use results simply because they are displayed—identify stable conditions before recording to reduce re-measurements and backtracking. High-precision positioning offers both speed and quality, but standardized operations are required to realize that.

If you want to make site position checks and simple surveying more agile and more practical, establishing a mobile positioning environment is meaningful. LRTK, as an iPhone-mounted GNSS high-precision positioning device, is a compatible option for situations where you want to streamline on-site position acquisition, recording, and sharing. For those who want to implement CLAS and other high-precision positioning concepts into practice and create a measurement environment that is easy to use on site, considering LRTK as an operationally feasible option alongside CLAS can make practical simple surveying easier to carry out.