Can soil volume calculation be done with drone surveying? Organizing the practical procedures into 5 steps

Table of Contents

• Can earthwork volume calculations be performed with drone surveying?

• Basic concepts to keep in mind for earthwork quantity calculations

• Operational procedure 1: Decide the purpose of the calculation and the criteria for comparison

• Practical Procedure 2: Accurately acquire the existing topography

• Operational Procedure 3: Preparing terrain data for use in calculations

• Work Procedure 4: Create a comparison surface and calculate soil volume

• Operational Procedure 5: Verify the results and incorporate them into on-site operations

• Precautions when calculating earthwork volumes with drone surveying

• Situations Where Drone Surveying Is Suitable for Earthwork Volume Calculations

• Summary

Is it possible to calculate earthwork volumes with drone surveying? This is a question that practitioners involved in civil engineering, land development, spoil management, material yards, extraction sites, temporary storage sites, and the like very often have. In short, drone surveying can certainly be used to calculate earthwork volumes. In fact, on sites above a certain area where you want to capture elevation differences and area-wide changes in cut and fill, it is an effective method for quickly and broadly identifying volume changes that are difficult to grasp with traditional point-based measurements alone.

However, it should be noted that simply flying a drone and photographing the ground does not automatically produce accurate earthwork volumes. The accuracy of volume calculations is affected by many assumptions and conditions, such as flight method, ground visibility, how reference coordinates are obtained, the definition of the calculation target, the approach to defining the surfaces to be compared, and the handling of extraneous objects. In other words, drone surveying is a powerful tool for calculating earthwork volumes, but the reliability of the results depends greatly on how operational procedures are organized.

Many people searching for this topic want not only to know whether earthwork volume calculations can be done with drone surveying, but also how to proceed on site, where errors are likely to occur, and what criteria to use to make judgments. Therefore, in this article we organize the concepts behind earthwork volume calculation using drone surveying, and then clearly explain the practical procedures divided into five steps. We explain from a field perspective without relying too heavily on technical jargon so that even those handling it for the first time can grasp the workflow.

Can drone surveying be used to calculate earthwork volumes?

It is possible to calculate earthwork volumes using drone surveying. This is because photos and terrain data acquired from above can be used to recreate the three-dimensional shape of the ground surface, and by comparing that surface with another reference surface or design surface, volume can be calculated. For example, it can be used to determine differences before and after earthworks, calculate the volume of temporary soil stockpiles, or assess the amount of fill during construction.

Common practice is to compare the existing ground surface with the planned ground surface to see where and how much cut and fill will occur. In some cases, the same area is surveyed at regular intervals to manage increases and decreases in soil brought in or removed. It is also used to determine the inventory of crushed stone and soil piled in stockyards.

Although its applications are wide, the essence of earthwork volume calculation is very simple. You prepare two surfaces to compare and accumulate their difference as a volume. What matters is that the two surfaces are handled in the same coordinate system and the same reference datum, and that irrelevant objects are not mixed into the comparison. If this is compromised, the figures may look plausible but will be unusable in practice.

Drone surveying makes it easy to capture wide areas in a short time, but it has the drawback of performing poorly in places where the ground surface is not visible. Areas covered by vegetation, water surfaces, or spots shaded by structures are unsuitable for earthwork volume calculations as-is. Therefore, drone surveying is not a panacea; it is important to assess whether the target terrain’s conditions are appropriate before using it.

Fundamental Concepts to Grasp for Earthwork Quantity Calculations

To correctly perform earthwork volume calculations, you must first clarify what you are comparing to derive the volume. In practice, there are three main approaches. The first is the method of comparing the existing surface with the design surface. On sites with development or grading plans, this method is the most fundamental. By aggregating the differences between the existing elevations and the planned elevations across the entire area, you can determine the cut and fill volumes.

The second method involves comparing existing surfaces captured at different points in time. For example, you survey the same location at different times—before and after construction starts, or at the beginning and end of a month—and calculate the differences. It is effective on sites where deliveries and removals are repeated and on sites where progress needs to be managed. Because the amount of change can be determined even without design drawings, it is also suitable for inventory management and process/schedule management.

The third method is to assume a reference plane and calculate the volume of a single mound or excavation. For example, for a pile of earth you calculate the volume above a reference such as the surrounding ground or an arbitrary base surface. Although this method appears simple, the result will vary depending on what is regarded as the base, so it is essential to establish rules in advance.

Even more important is that the term "soil volume" is not always used with the same meaning. It can refer to the volume of the in-situ ground before and after excavation, or to the apparent volume of the soil that has been transported. Because the required level of granularity and the allowable error vary depending on the purpose—construction management, as-built verification, preliminary cost estimation, inventory control, etc.—the degree of precision demanded for the same soil volume calculation differs. Simply clarifying at the outset whether the figures are intended for on-site use or are reference values for internal review will greatly reduce confusion in downstream processes.

Practical Procedure 1: Define the Purpose of the Calculation and the Comparison Criteria

The first step is to clarify the purpose of the earthwork quantity calculation. If you start surveying while this remains unclear, you are likely to encounter problems later, such as lacking necessary data, inconsistencies in how reference surfaces are created, or being unable to use the results for on-site explanations.

For example, the data you need to prepare will vary depending on whether you want to know the cut and fill volumes for a site development plan, to understand the increases and decreases before and after construction, or to determine the inventory of temporarily stored soil. If comparing with the design, you need to provide the design surface; for time-series comparisons, you must survey the same extent and use the same reference each time. If you are assessing stock volumes, a key issue is how to define the bottom surface.

At this stage, the four things you should decide are the scope of calculations, the comparison basis, the required level of accuracy, and how the results will be used. If the scope of calculations is not clear, whether to include or exclude slopes or how much of the surrounding work roads to include will vary from person to person. If the comparison basis is not decided, it becomes ambiguous whether the comparison is current versus planned, current versus current, or a standalone volume. If you do not determine the required accuracy, you may expend excessive effort when a rough assessment would suffice, or conversely rely on a crude method when a precise check is needed. If the intended use of the results is clarified, it becomes easier to decide whether to produce reports, create drawings, or simply share them internally.

Also, in practice the boundary conditions of the calculation target are often overlooked. For example, if the edges of an embankment area are not clearly defined in the field, the calculated volume will change depending on how far you include in the calculation range. If you perform calculations while the slope crest or slope toe is ambiguous, the figures will not match the site later. Therefore, at the stage of field verification, decide whether to cut the boundary by physical features, by drawings, or by an imaginary line; doing so stabilizes practical work.

Furthermore, it is important for those in charge to align on the definition of earthwork quantities. Even at the same site, purposes can get mixed: the construction staff may want to use them for progress payments, the design staff to compare them with future plans, and the management staff to verify consistency of material haul-in and haul-out. If understandings diverge later, even a carefully conducted survey can lead to the figures being used inconsistently. That is why the first step should not be to skip this, but to articulate the purpose of the earthwork quantity calculation.

Work Procedure 2 Accurately Capture the Existing Terrain

The next step is to correctly capture the existing terrain. The foundation of earthwork volume calculations from drone surveying lies in the quality of the existing surface. If the acquired terrain is coarse, incomplete, distorted, or has unstable coordinates, no matter how carefully subsequent calculations are performed, their reliability will not improve.

When acquiring the current terrain, it is important to plan flights so that the calculation target can be captured sufficiently from above. In earthwork volume calculations, reproducibility of the surface shape is critical, so if image overlap is insufficient or slopes and faces of embankments are not fully captured, the quality of the terrain model will decline. It is necessary to reliably capture not only flat ground but also locations with large shape changes, such as cut slopes, fill slopes, excavation areas, and places with level differences.

Also, the conditions during capture affect the results. Strong winds tend to impact the stability of the aircraft and image quality, and when ground patterns are difficult to see the accuracy of 3D reconstruction can decrease. Furthermore, if large vehicles, heavy machinery, people, materials, or tarpaulins are scattered across the site, they can be incorporated as terrain, causing the estimated soil volume to appear greater or smaller than it actually is. When the goal is soil volume calculation, it is ideal to choose a time with as few extraneous objects as possible.

Additionally, alignment with control points and known points is also important. In earthwork quantity calculations, results from two or more surveys are often compared or overlaid with the design surface, so if the horizontal and vertical reference frames are not stable the differences are meaningless. You need to pay attention not only to the overall horizontal alignment of the site but also to consistency of the vertical datum. Even when things appear to overlap visually, a small vertical offset can substantially change the earthwork quantities. This is especially true for large sites or those with significant elevation differences, where how you establish references directly determines the results.

In practice, it is helpful to take verification photos and keep on-site notes during the data acquisition stage. Information about where puddles were, where materials were placed, and the extent of grass growth can provide useful reference for post-processing and verification. Drone surveying is efficient, but if it is completed only on-screen without visiting the site, non-topographic objects can be mistaken for terrain. Linking the actual site conditions with how the data appears is essential for accurate earthwork volume calculations.

Practical Procedure 3: Preparing Terrain Data for Use in Calculations

After acquiring the current topography, you should not use it directly for earthwork volume calculations; you need to process it into terrain data suitable for calculation. If this process is neglected, you may obtain figures that are difficult to explain.

The first thing to do is to separate the surfaces that should be used as terrain from those that should be excluded. For example, vehicles parked on site, stored materials, temporary structures, heavy equipment in operation, and surrounding features unrelated to the fill that are included in the model should, in principle, be excluded. If you leave these in when performing volume calculations, the resulting figure will include the volumes of objects temporarily present on site rather than the actual volume of soil at the site.

Another important consideration is the continuity of the terrain surface. The acquired data may include parts that are not visible due to shadows or areas where the ground texture is too weak for stable reconstruction. If such areas remain as holes or undulations, they introduce noise into volume calculation results. It is necessary to perform interpolation or editing as appropriate and to adjust the surface so it does not look unnatural when compared with on-site conditions. However, excessive editing increases the amount of inferred data relative to actual measurements, so it is also important to clearly define how far to correct and when to decide a re-survey is required.

Furthermore, in earthwork volume calculations it is important to be aware of the type of ground surface. Whether it is grassland, bare ground, a paved surface, or a surface covered with a sheet will affect whether the captured surface is truly the surface you want to calculate. For example, in areas with deep grass, what is visible may be close to the top of the vegetation rather than the actual ground. If that is treated as the existing surface, it will appear thicker than it actually is. Drone surveying fundamentally captures the visible surface and does not automatically guarantee the unseen true ground.

When comparing data from multiple time points, it is very important to align them under the same processing policy. If you remove unwanted items rigorously only on the first occasion and use a simplified procedure thereafter, the differences will be mixed with inconsistencies from the processing approach. If you will be continuously monitoring the same site, standardizing how you delineate the area of interest, exclusion criteria, correction rules, and output formats will improve comparability.

In short, this step is not merely data organization. It is the process of redefining the terrain that will be used for calculations. By clearly specifying what to retain and what to exclude, how far to regard data as actual measurements and from where to treat it as corrections, the subsequent earthwork volume calculations and accountability become much more reliable.

Work Procedure 4 Create a comparison surface and calculate earthwork volume

Once the terrain data are prepared, it's time to create the comparison surface and calculate earthwork volumes. In this process, which surface you use as the reference greatly influences the results. It is important to choose the comparison method according to your objective, such as existing conditions vs. design, existing conditions vs. previous conditions, or an isolated mound vs. an assumed base surface.

For an as-built vs. design comparison, overlay the design surface and the existing surface to the same datum and calculate the elevation difference at each location. If the existing surface is higher than the design, it can be classified as cut; if lower, as fill. What is important here is interpreting the design surface to match site conditions. If items such as slope layout, edge detailing, or the handling of interim construction-stage surfaces are ambiguous, a simple difference alone will produce results that are not practical. Confirming whether the design shows only the final shape or whether you want to include intermediate stages in the comparison will yield more usable figures.

When comparing the current condition with a previous one, the same area is compared using the same coordinate reference and the amount of increase or decrease is calculated. This method is suitable for progress management, but if survey conditions vary each time, errors can easily creep into the differences. For example, if temporary materials are placed where there were no materials last time, that will also appear as an increase. Therefore, in time-series comparisons, operational rules are indispensable to determine which changes in site conditions to include in the differences and which to exclude.

When determining the volume of an individual heap or stockpile, the definition of the base surface is the main issue. Whether you take the base as the surrounding ground, the compartment’s management height, or a known elevation for the entire storage area will change the calculated volume. In other words, the volume of a single pile is not only a surveying or measurement issue but also a matter of operational definition. If the method will be used continuously on site, it is important to calculate using the same base rule every time.

The results of earthwork volume calculations are more useful in practice if, rather than looking only at the total volume, you separate cut and fill quantities as needed, divide them by ranges or zones, or view them by construction block. Because many sites find it difficult to translate only the overall value into a work plan, organizing the data so you can see how much each section increased or decreased will also be helpful in progress meetings and when sharing with stakeholders.

Also, although earthwork quantities can be displayed with precision down to decimal places, the ability to display that level of detail is not the same as the meaningfulness of it. For figures used on site, it is more practical to decide the rounding method and the number of displayed digits according to the required precision. Overly detailed numbers can, conversely, give an impression of excessive accuracy. Because earthwork quantities are affected by surveying, terrain conditions, processing conditions, and reference-surface settings, do not overtrust the results; formatting them to suit their intended use is also part of practical work.

Operational Procedure 5: Validate Results and Implement Them into On-site Operations

Earthwork quantity calculations are not finished once the numbers are produced. The final step is to verify whether those results can be used on site and to incorporate them into operations. If you skip this step, you'll end up with numbers that no one can confidently use.

First, what we want to do is verify consistency with on-site intuition. If the site personnel see and feel that something is obviously too large or too small, there may be a problem with data processing or with the settings used for comparison. Of course, you should not judge solely based on human intuition, but the sense that something is off held by people who know the site is an important checkpoint. In particular, slope faces, corner areas, heavy equipment work zones, and areas around temporarily stored materials are prone to errors, so it is advisable to check them carefully.

Next, checking at representative points is effective. By confirming the surface elevation at some representative locations and checking whether they differ significantly from known elevation data or measurements obtained by other methods, it becomes easier to assess the overall validity. Even if it is not necessary to remeasure the entire area by another method, confidence in the results increases if key locations are consistent.

Also, creating difference maps and checking cross sections makes it easier to detect anomalies that numbers alone do not reveal. Even if the total soil volume looks plausible, localized, unnatural bulges or depressions in specific areas can indicate disturbances in the terrain model or the inclusion of unwanted material. When using this for ongoing management in particular, keeping the verification diagrams in the same format each time makes it easier to compare with past data.

Furthermore, reproducibility is important in the operation of earthwork volume calculations. To ensure that the same approach yields consistent results even when personnel change, it is effective to document—even briefly—the rules for setting extents, the criteria for excluding unwanted materials, the approach to defining the bottom surface, and the method for summarizing results. It may feel like extra work at first, but from the second time onward the quality of the work will stabilize and it will be easier to explain.

When implementing this in on-site operations, you need to consider who will use the earthwork volume calculation, when they will use it, and for what purpose. Whether it is used to monitor construction progress, for internal reporting, or for managing material in/out will determine how the results need to be summarized. In some cases it is better to share the terrain data itself, while in others the numbers alone are sufficient. In other words, earthwork volume calculation is not merely an analytical task but the preparation of information for decision-making. It only becomes valuable when presented in a form that can be used on-site.

Precautions when Calculating Earthwork Volumes in Drone Surveys

We have reviewed the procedures up to this point, but in practice it is important to understand several points of caution. First and foremost, drone surveying is a technique that deals with visible surfaces, so it has the limitation that areas beneath vegetation, under coverings, or below the water surface cannot be accurately captured as-is. Therefore, you must always verify that the target is truly the soil surface.

Additionally, earth volumes are an accumulation of small differences in elevation. Across a large area, even a deviation of a few centimeters can produce a significant difference in volume. Therefore, consistency of the elevation reference—not just planar position—is very important. Whether comparing existing conditions with each other or with the design, if the reference is unstable the differential results become difficult to trust.

Next, you should also be aware that the way the target area is delineated can affect the results. For example, whether you cut the area partway down the slope or include the slope toe will change the total volume. The surveyed area may shift slightly due to site conditions, but if you are making ongoing comparisons, it is essential to keep the area consistent.

Furthermore, when you directly link the results of earthwork volume calculations to transported quantities or contract quantities, you need to be careful about differences from the definitions used in practice. In-situ volume, loosened soil volume, and compacted volume are not the same. Using the volume obtained from drone surveying without understanding which state of volume it corresponds to will cause discrepancies with on-site figures. Volume calculations are extremely useful, but it is important to explicitly state what volume you are looking at when using them.

Situations Where Drone Surveying Is Well-Suited for Earthwork Volume Calculations

Volume calculations using drone surveying are not equally suitable for every site. They are well suited to sites where you want to capture a relatively wide area in plan, sites where you need to perform repeated surveys over a short period, and sites where you want to safely assess areas that are difficult to access.

For example, in earthworks for site development, it is well suited to understanding cut-and-fill by comparing the existing ground surface with the planned grade. At temporary storage yards, it is easy to use for managing stock quantities over regular intervals. At extraction sites and spoil disposal areas, it also helps capture trends in material inflow and outflow volumes. Even in locations with many slopes and steps, capturing the area from above makes it easier to grasp the overall picture of terrain changes.

On the other hand, in confined spaces with many surrounding obstacles, where the ground surface is not visible, in areas covered by trees or structures, or when you need to trace extremely fine shapes with high precision, it can be better to combine alternative measurement methods or complementary techniques. Using the most suitable method for the site conditions is ultimately the most rational approach.

Summary

You can calculate earthwork volumes using drone surveying. In practice, major advantages are that it makes it easy to grasp large areas in a short time, to track changes over time, and to make decisions while viewing the entire site as an area. However, simply flying and generating data is not enough to obtain correct results. It is important to decide what the calculation is for, appropriately acquire the current topography, prepare the terrain surface to be calculated, compute volumes using comparison surfaces suited to the purpose, and finally verify the results and integrate them into site operations.

To summarize once more the practical procedures organized here: first define the calculation purpose and comparison criteria; next correctly acquire the current site topography; then prepare the data for calculation, create the comparison surface, and calculate the earthwork volume; finally verify the validity and convert the results into usable deliverables. If you follow this flow, earthwork volume calculations from drone surveys can be used not merely as reference values but as information that supports on-site decision making.

Also, to operate earthwork volume calculations reliably, not only the process of capturing terrain from the air but also the management of ground-based references is important. If position and elevation references are ambiguous, no matter how visually impressive the 3D data you produce, it will be difficult to have confidence in the differencing results. If you want to streamline routine on-site positioning and reference checks, reviewing ground-side operations can also lead to major improvements.

In that regard, if you want to streamline on-site stakeout, control point checks, and as-built verification together with drone surveying, the idea of combining an iPhone-mounted high-precision GNSS positioning device like LRTK is also effective. When the broad, aerial surveying work connects with the work of accurately confirming positions on the ground, it becomes easier to establish the prerequisites for earthwork volume calculations and to carry out on-site verification. For those who want to put drone surveying results to more practical use in the field, setting up this kind of ground positioning system as well makes it easier to improve the overall accuracy and speed of operations.