5 criteria for deciding when to combine a total station with point cloud surveying

A total station is a surveying instrument used in situations where you want to verify control points and survey points one by one on site. On the other hand, point cloud surveying is well suited to recording the shapes of objects and terrain as surfaces, and can be used for as-built verification, understanding current conditions, and comparing before-and-after construction. Rather than thinking in terms of just one or the other, being able to decide how to combine a total station and point cloud surveying can improve the explainability of survey deliverables and the efficiency of field work. In this article, we organize the decision-making for combined use—something practitioners often find confusing on site—into five criteria.

Table of Contents

• Clarify the objectives of combining a total station and point cloud surveying.

• Decision Criterion 1: Do you prioritize the reliability of control points and coordinate management?

• Decision Criterion 2: Does the area require planar shape recognition?

• Judgment Criterion 3: Are results that are easy to explain in inspections and consultations required?

• Assessment criterion 4: Are the on-site conditions suitable for point cloud acquisition?

• Evaluation Criterion 5: Can work procedures and the organization of deliverables be implemented without undue burden?

• Operational checks to prevent failures during concurrent use

• Summary: Use total stations and point cloud surveying by assigning roles

Organizing the Objectives of Combining a Total Station and Point Cloud Surveying

The first thing to consider when using a total station together with point cloud surveying is the purpose: why are they being combined? Because point cloud surveying can record site shapes as surfaces, it is useful for grasping wide-area topography, the outlines of structures, slopes, excavated faces, embankment surfaces, and pavement surfaces. However, even if you only acquire point cloud data, if its position is not properly managed relative to the site’s control coordinates, it can become difficult to treat as a survey deliverable. By combining control point surveys and verification surveys using a total station, it becomes easier to clarify the positioning of the point cloud data.

The total station is well suited to tasks that involve selecting survey points and measuring distances and angles to manage coordinates and elevations. Point cloud surveying is well suited to tasks that acquire many points at once and verify the shape as a surface. Understanding this difference makes it easier to organize how to use them together. The total station makes it easy to clarify "which point to use as a reference" and "which points to use as checkpoints," while point cloud surveying is an easy way to grasp "what the surrounding shape is like."

For example, if you record the current conditions before construction as a point cloud and later want to use it for construction planning or as‑built verification, checking the site’s reference and control points with a total station makes coordinate management of the point cloud data easier. Also, when you want to identify important positions from the point-cloud-derived geometry—such as boundaries, the top edge, slope shoulder, slope toe, and corners of structures—establishing the necessary survey points with a total station makes it easier to explain the reliability of the results.

On the other hand, it is not always necessary to use both methods at every site. If the objective can be achieved with only small-scale positioning or if point-based verification is sufficient, work centered on a total station may be enough. Conversely, if the goal is to record the site's overall undulations and the shapes of structures as surfaces, there is greater value in utilizing point cloud surveying. What is important is not to decide the working method in advance, but to work backward from the required deliverables and allocate the roles of the total station and point cloud surveying accordingly.

If work is started while the purpose of using both methods is unclear, even if point cloud data is acquired, problems tend to arise: you may not know which points to use as the basis for explanations during inspections or consultations; the points measured with the total station may not be reconciled with positions on the point cloud; and it can be difficult to correlate the results drawings with record photos. Conversely, if the purpose is clarified at the outset, it becomes clear which points should be measured with the total station, the extent that should be recorded with the point cloud, which photos should be taken on site, and which items should be organized in post-processing.

Therefore, when considering combined use, it is important to first separate "information you want to manage as points" from "information you want to capture as surfaces." Adopting the approach of verifying with a total station the items that need to be clearly retained as coordinate values, and recording with point-cloud surveying the items whose shape continuity and surrounding conditions you want to preserve, makes on-site decision-making easier.

Criterion 1: Do you prioritize the reliability of control points and coordinate management?

The primary criterion for combining an optical total station and point cloud surveying is how much emphasis you place on the reliability of control points and coordinate management. Point cloud surveying can capture a large number of points to recreate site geometry, but if it is unclear which coordinate system the point cloud is based on or how it ties to the site control, it becomes difficult to handle in practice. Especially when the data are used as supporting documentation for construction management, as-built verification, or justification for design changes, not only the apparent shape but also the management of position and elevation is important.

A total station plays a role in supporting on-site coordinate control through observations from known points, resection (back intersection), and checks between control points. Before conducting point cloud surveying, measuring the site’s control points, calibration points, and check points with a total station makes it easier to organize the reference information when aligning point cloud data to coordinates. If the coordinates of the points used to align the point cloud are uncertain, doubts will remain about the position of the entire acquired point cloud. Therefore, the more critical coordinate control is on a site, the more valuable it is to plan on using a total station in conjunction.

For example, in road construction, site development, river works, and construction around structures, positional relationships from control points and elevation control are directly tied to the reliability of the deliverables. Even if a large area is recorded by point cloud surveying, if you cannot explain which control points it is based on or at which check points the accuracy was verified, it will be difficult to make judgments when reviewing the deliverables later. Verifying control points and key points with a total station and linking that information to the point cloud data makes the deliverables easier for on-site stakeholders to trace back to their basis.

Also, in point cloud surveying, the density and accuracy of the point cloud vary depending on the instrument setup locations at the time of acquisition, the placement of control points, the distance to the target, line-of-sight conditions, and so on. Even data that appears spatially consistent can be difficult to use for construction management decisions if it is not aligned with reference points. By establishing check points with a total station, it becomes easier after creating the point cloud data to verify whether specific positions or elevations are not significantly offset from the site reference.

When prioritizing control points and coordinate management, you need to decide during the planning phase of their combined use which points will serve as control points, which will be used for point cloud alignment, and which will be reserved for result verification. If control points and check points are treated as the same, the basis for later accuracy verification can become weak. Separating the points used for point cloud alignment from those used to verify the alignment afterwards provides reassurance when explaining the results.

When combining coordinates measured with a total station and point cloud data, it is also important to standardize the coordinate system, height datum, units, point names, and the meaning of survey points. If point names vary by site or explanations of the survey points are not recorded, it becomes difficult for the recipient of the data to understand the content. Surveying deliverables are not something that only the person who collected them needs to understand; personnel in later stages, partner companies, clients, and inspectors may also need to check them. Therefore, it is important to record the correspondence between the survey point information obtained with the total station and the point cloud data in a way that remains understandable later.

Evaluation Criterion 2: Is this an area where understanding surface geometry is necessary?

The second criterion is whether it is necessary to capture the shape of surfaces on site. Total stations are well suited to the task of checking selected survey points, but to capture fine undulations or continuous shapes over a wide area they often require a large number of points, which can increase the workload. Point cloud surveying can acquire the surfaces of terrain and structures as large numbers of points, making it effective when you want to verify surface changes.

For example, the shape of embankments and cuttings, irregularities on slopes, the finished condition of excavation faces, undulations in pavement surfaces, and the interfaces around structures are items that are easy to overlook if understood only by points. Measuring only representative points with an optical total station can make it difficult to confirm local irregularities or steps between those points. By combining point cloud surveying, the site’s shape can be verified as a surface, making it easier to use for pre- and post-construction comparisons and for explaining as-built conditions.

However, recording surfaces with point cloud surveying is not necessarily sufficient. Point cloud data will have areas that are visible and areas that are hard to see depending on acquisition range, point density, occlusions, reflection conditions, and the condition of the target. Vegetation, materials, heavy machinery, temporary structures, and the movement of people can hide the surfaces you actually want to check. In such cases, supplementing the point cloud by measuring key points with a total station can capture positions that are difficult to confirm from the point cloud alone.

When determining whether it is necessary to capture surface geometry, consider what you want to explain as the deliverable. If the sole purpose is simply to "record the site conditions," extensive coverage by point cloud surveying is effective. On the other hand, for judgments such as "how does the elevation at this location compare to the design value," "does this boundary coincide with the planned line," or "is the corner of this structure at the specified position," confirming points with a total station is important. Separating what should be viewed as surfaces and what should be confirmed as points is the basic principle for deciding to use both methods.

Even when the site area is large, the combined approach tends to be more effective. If you try to measure every detail of a wide site or a long alignment using only a total station, the work takes a long time and organizing the survey points becomes complicated. By using point-cloud surveying to capture the overall shape and a total station to measure control points and important management points, it becomes easier to balance overall understanding with management of reference points. In particular, if you want to check arbitrary cross-sections later or see differences before and after construction, it is worthwhile to retain the point-cloud data.

On the other hand, for tasks where the objective can be achieved by checking only a few points within a narrow area, combining point-cloud surveying may only increase the post-processing workload. For example, for simple layout setting, checking the heights of a small number of points, or verifying locations whose shapes have already stabilized, workflows centered on total stations can be more efficient. Whether to use point-cloud surveying should be decided not because you want to use new equipment, but based on whether area-based information is necessary for making judgments.

Evaluation Criterion 3: Is an outcome that is easy to explain during inspections and consultations required?

The third criterion is whether results that are easy to explain during inspections or consultations are required. Survey deliverables are used not only to advance work on site but also for consultations with the client, consideration of design changes, confirmation of as-built conditions, construction records, handover materials, and so on. In such cases, simply having the data is not enough; it is important to be able to explain which standard was used for the measurements, what scope or extent was recorded, and which survey points serve as the basis for any judgments.

Total station surveying makes it easy to organize point names, coordinates, elevations, observation dates, observation conditions, and so on, and is a convenient method when explaining specific survey points. On the other hand, point cloud surveying makes it easy to visually show the overall shape of the site and can supplement situations that are difficult to convey with photos or drawings alone. Using both together allows you to combine numerical explanations with shape-based explanations, making it easier to enhance the clarity of consultation materials.

For example, if the pre-construction ground shape differs from the assumptions made during design, verifying representative survey points and control sections with an optical total station and showing the surrounding terrain as a point cloud makes it easier to explain the extent and trends of the differences. Coordinates of representative points alone may not fully convey changes across the entire site. Conversely, a point cloud image alone can leave unclear which position is being used as the reference for judgment. By combining the survey points from the optical total station with the surface information of the point cloud, you can explain both the numerical values and the shape.

When producing deliverables for inspections, it is important not to rely solely on the visual appearance of point cloud data. Because point clouds are visually easy to understand, there is a temptation to explain things based on how they look on the screen, but inspections may require demonstrating the relationship to measured points and reference benchmarks that provide the basis for the assessment. Showing the points verified with a total station alongside the point cloud makes it easier to explain which location was checked against which reference.

Also, for meetings and inspections, it is important that records can be verified later by third parties. Even information that the site person in charge can explain verbally will become vague over time. If you organize point cloud data, lists of survey points, site photographs, work notes, and information about the control points used, it will be easier to follow the flow of decisions when reviewing them later. If you associate the points measured with a total station with the positions in the point cloud, you can also reduce rework when preparing documentation.

To make the deliverable easy to explain, you need to envision its form from the start. If you simply capture whatever you can on-site and try to organize it later, required points may be missing, the point cloud may have blind spots, or you may be unable to correlate the photos. If you plan to use the data for inspections or consultations, decide before starting work "which drawings to overlay it on," "which cross-sections to use for verification," "which survey points to present as the basis," and "which area of the point cloud to use as the deliverable," as this will make combined use more effective.

Judgment Criterion 4: Are the site conditions suitable for point cloud acquisition?

The fourth criterion is whether the site conditions are suitable for point cloud acquisition. Point cloud surveying is a convenient method for obtaining surface information, but depending on site conditions it can be difficult to acquire sufficient data. When considering combining it with a total station, it is important to confirm whether point cloud surveying can function effectively in the environment and, if necessary, plan to supplement it with the total station.

In point cloud surveying, it is fundamental that the object be visible. Parts not visible from the instrument, areas hidden by obstacles, surfaces that do not reflect well, and places with many moving objects can cause gaps or noise in the point cloud. When a site contains many materials or heavy machinery, the acquired point cloud may include unwanted items, making the ground surface or structural surfaces you want to inspect difficult to see. In such sites, it is safer not to rely solely on point cloud surveying and to verify important control points with a total station.

Also, at confined sites or sites with large elevation differences, the placement of and capture directions for point cloud surveys can be restricted. If a target can only be seen from one direction, blind spots will occur on its rear or in the shadow of offsets. Acquiring point clouds from multiple positions can reduce blind spots, but it also increases the work required for registration and data organization. If you set control points and check points with a total station, managing the alignment of multiple point cloud datasets becomes easier.

Weather and the working environment should also be factors in the decision. Rain, fog, strong winds, intense sunlight, dust, and mud splashes, among other conditions, affect surveying operations overall. Both total stations and point cloud surveys must be used only after ensuring the stability of instrument setup, line of sight, the visibility of the target, and the safety of personnel. In particular, because point cloud surveying records a wide area at once, frequent movement of heavy equipment or workers during acquisition can easily cause unwanted points or gaps. Decisions such as adjusting working hours or dividing the acquisition area are necessary.

Having conditions that are unsuitable for point cloud surveying does not mean you need to give up using both methods together. Rather, a division of roles is effective: use a total station to supplement parts that are difficult to capture with point clouds, and use point clouds to record broad surfaces that are hard to grasp with a total station alone. For example, in areas with many obstacles, one approach is to record the overall spatial relationships with point clouds while separately verifying important points that are likely to be hidden with a total station. In places with large shape changes, such as slopes or around structures, it becomes easier to organize the data by acquiring surfaces with point clouds and using a total station to fix control points like crests and edges.

When assessing site conditions, you need to consider not only the quality of the data after acquisition but also the safety of the work. If the place to set the equipment is unstable, if it is close to the traffic routes of vehicles or heavy machinery, or if work at heights or near the water’s edge is required, it is more practical to determine the range that can be captured from safe positions and fill in the missing parts by other methods rather than forcibly increasing point cloud acquisition locations. Both total stations and point cloud surveying should be used on the premise of site safety management.

Evaluation Criterion 5: Can work procedures and the organization of deliverables be operated without undue burden?

The fifth criterion is whether the work procedures and the organization of deliverables can be operated smoothly. Using a total station together with point-cloud surveying increases the amount of information that can be obtained, but it also increases the burden of on-site arrangements, data management, post-processing, and organizing deliverables. Whether combining them is effective depends not only on the performance of the equipment but on whether the procedures can be translated into workflows that field personnel can actually operate.

First and foremost, the order of on-site tasks is important. You need to organize in advance the sequence of checking control points, installing reference and check points, observing survey points with a total station, acquiring point cloud data, photographic documentation, post-processing, and results verification. If you work with an unclear sequence, problems are likely to occur, such as having acquired the point cloud but lacking coordinates for the reference points, forgetting to photograph the check points, or the measurement point names not matching positions on the point cloud.

Next, naming and storage methods for data are also important. If measurement point data from total stations, point cloud data, site photos, work records, drawings, and deliverable files are stored separately and their relationships become unclear, organizing the deliverables later will take more time. It is necessary to establish rules for the date, site name, survey area, scope of work, measurement point names, etc., and to manage related data using the same conventions. In particular, when multiple people are working, it is important to ensure that naming does not vary by person in charge.

The burden of organizing deliverables also has a major impact on the decision to use them in combination. Point cloud data contain a large amount of information, so simply acquiring them can make them difficult to use as practical deliverables. Processing according to the purpose is required, such as removing unnecessary points, aligning coordinates, creating cross-sections, checking quantities, comparing with drawings, and matching lists of survey points. The outputs of total stations also need observation data, coordinate calculation results, point names, and control point information to be clearly organized, otherwise they become difficult to treat as combined results with point clouds.

To operate combined use smoothly, it is important not to try to do everything at an advanced level from the outset. By defining, according to the site’s purpose, the minimum required control points, checkpoints, point cloud extent, and deliverable formats, you can prevent the work from becoming overly complex. For example, if the goal is to compare pre- and post-construction conditions, prioritize ensuring that you can capture the same area using the same references. If the purpose is as-built verification, clarify the measurement points and cross-sections to be compared with the design values. If the purpose is materials for discussion, organize the area to be used for explanation and the reference points that support it.

It is also necessary to have a mechanism that allows site personnel to verify the results. Even if the processing of point cloud data is left solely to specialists, verifying the results becomes difficult unless the site personnel understand "which areas were captured," "which points were used as references," and "which points were designated as check points." When combining total stations and point cloud surveys, it is essential to keep work records on the premise of information sharing between the field and processing teams.

From the perspective of practical operation, care must be taken not to let increasing equipment or methods become an end in itself. If using them together makes on-site decision-making clearer, reduces rework, makes it easier to prepare explanatory materials, or makes it easier to reconfirm conditions later, then combining them is worthwhile. Conversely, if the intended use of the outputs is unclear and only the burden of data organization increases, you should reconsider whether work centered on a total station or records of point-cloud surveying alone would be sufficient.

Practical Checks to Prevent Failures During Combined Use

When combining total station surveying and point cloud surveying, it is effective to separate checks into before, during, and after work to prevent failures. Before work, decide on the objectives, target area, control points, check points, point cloud acquisition locations, and deliverable formats. In particular, it is important to clarify the relationship between the point cloud survey’s capture area and the measurement points to be measured with the total station. If check points are biased outside the area recorded by the point cloud, or if there are no check points around important structures, it will be difficult to verify the consistency of the results later.

During work, confirm that the conditions visible on site match the recorded information. On the spot, verify where the points measured with the total station are located, whether the control points and check points for the point cloud survey can be identified in the photographs, and whether there are any areas obscured by obstacles; doing so makes it easier to decide whether a re-survey is necessary. If you notice missing data after leaving the site, a revisit may be required, which can affect the project schedule.

After the work, verify the consistency between the survey point data from the total station and the point cloud data. Check whether the coordinates, elevations, and point names of control points and check points match, whether the points used for aligning the point cloud and the points used for verification are properly organized, and whether there are any gaps or extraneous objects within the area to be used as the deliverable. Because point cloud data contains a large amount of information, it is important not to judge by appearance alone but to confirm using the necessary cross-sections and survey points.

Furthermore, it is important to organize the deliverables so that others can verify them. Survey results may be viewed not only by on-site personnel but also by later-stage designers, construction managers, and inspectors. By clearly indicating which control points were used, which area was captured as a point cloud, which survey points were checked with a total station, and which data constitute the final deliverable, you can reduce inquiries and rework.

A common problem when using them together is that people become overly focused on acquiring point cloud data and delay organizing control points and check points. Because point clouds are visually intuitive, it may feel as though the site conditions have been recorded, but to use them as surveying deliverables, coordinate management and verification of control points are indispensable. The total station plays a role in providing that basis. To make the most of the convenience of point cloud surveying, it is important not to neglect control management with the total station.

Also, it is important not to treat the results of point cloud surveying and total station surveying as separate. If point clouds remain as point clouds and survey points remain as survey points, the benefits of using them together will not be fully realized. By linking the locations you want to verify on the point cloud with the points measured by the total station, surface information and point information become connected. This makes it easier to explain site conditions, verify quantities, compare before-and-after construction, and prepare inspection documentation.

Summary Use total stations and point-cloud surveying in complementary roles

When using a total station together with point cloud surveying, it's important to consider not which is superior but which information you will verify by which method. A total station is well suited to tasks of establishing reference points, control points, and check points. Point cloud surveying is suited to capturing the shapes of terrain and structures as surfaces and recording the overall condition of the site. Understanding this difference in roles makes it easier to decide how to use them together.

As evaluation criteria, it is important to confirm whether reliable control points and coordinate management are required, whether capture of surface geometry is necessary, whether deliverables that are easy to explain in inspections or consultations are needed, whether site conditions are suitable for point cloud acquisition, and whether work procedures and the organization of deliverables can be operated without difficulty. By organizing these in advance, the points to be measured with a total station and the areas to be recorded by point cloud surveying become clear, making it easier to reduce rework on site.

Especially when using point cloud data for construction management and as-built verification, the handling of control points and check points is important. Point cloud data can clearly represent surface conditions, but if its relationship to on-site control is ambiguous, it becomes difficult to explain as surveying results. By confirming the reference points with a total station and linking them to the point cloud data, you can describe the site from both numerical and geometric perspectives.

Even as the use of point cloud data expands, that does not mean the role of the total station disappears. There are cases where a total station is needed for control management and check surveys that support the results of point cloud surveying. Separating information verified at points from information recorded as surfaces, and combining them when necessary, is the approach suited to practical work.

When considering combined use on site, prioritize whether you can organize the data into a form that can be explained as a deliverable, rather than the amount of data acquired. If you can manage control points, check points, point-cloud extents, photos, and work records together, you will get closer to survey deliverables that are easy to use for construction management, coordination, inspection, and handover.