7 checks before converting total station measurement results into drawings

Measurement results obtained with a total station are not ready to be placed directly onto drawings as-is. The coordinate values and elevations, point names, notes, and observation conditions recorded on site contain many items that should be checked before drafting. Even if everything appeared fine at the time of measurement, it's not uncommon during the drawing stage to find misidentified control points, duplicate point names, mixed elevation datums, the inclusion of unnecessary points, incorrect line connections, and similar errors.

Especially when creating plans, as-built drawings, site plans, layout plans, cross-sections, longitudinal profiles, etc., using measurement results from a total station, insufficient checks before drafting the drawings directly lead to rework in later stages. Once something has been represented on the drawings, it takes time to distinguish which parts are observation errors, drafting mistakes, or inconsistencies with the design conditions. That is why it is important to review and organize the consistency of the field data before converting the measurement results into drawings.

Table of Contents

• Verify the consistency between the coordinate system and reference points

• Check for duplicate point names and survey point codes

• Confirm the handling of the vertical datum and instrument height.

• Check for anomalies and outliers in the observed values.

• Cross-check the meanings of field notes and measurement points

• Verify the connectivity of lines required for drafting.

• Confirm that the accuracy and presentation are suitable for the intended use of the deliverable drawings.

• Workflow for preparing total station measurement results before converting them into drawings

Verify consistency between coordinate systems and reference points

Before converting measurement results from a total station into drawings, the first thing to check is the alignment of the coordinate system and reference points. If you begin drafting while it is unclear which coordinate system the measured point data collected on site is based on, the entire drawing can be shifted, may not match existing drawings, and could require major revisions later. In particular, when overlaying with existing drawings, design plans, boundary documents, or coordinate data for construction management, confirming the coordinate system is a prerequisite to creating the drawings.

When measuring a site with a total station, you may set up the instrument using known control points, establish a backsight, and proceed with observations according to the site coordinates. At that time, you need to confirm that the coordinate values of the reference points used are up to date, that there are no errors in the numbers entered on site, and that the backsight direction is set correctly. If reference point names are similar or you are reusing coordinate data from a previous work section, mistakes are likely to occur if you judge only by the point names. Before drafting the drawings, compare the list of reference points used with the coordinate values in the measurement data to verify they match the references intended on site.

When checking the coordinate system, it is also important to know which approach is being used for management: the plane rectangular coordinate system, arbitrary coordinates, or site-specific coordinates. At construction sites, the contract drawings or design plans may be created using public coordinates, or they may be converted and managed in arbitrary coordinates that are easier to handle on site. Rather than saying one is correct, it is important to clarify which coordinate system should be adopted with respect to the intended use of the drawing deliverable. The reference standard to use will vary depending on whether the drawing is to be used as a submission deliverable, as an on-site reference drawing, or for verifying construction positions.

Also, when overlaying measurement results onto existing drawings, check whether the entire set is shifted uniformly or only a portion is displaced. If the whole has moved by the same amount, the cause may be differences in the coordinate system or origin settings. On the other hand, if only part of the site is significantly displaced, suspect causes such as incorrect input of observation points, swapping prism positions, improper backsight settings, or misinterpretation of the meaning of measurement points. Simply moving positions to align them at the drafting stage can overlook the root cause.

When verifying the consistency of reference points, check not only at the start of measurement but also at locations where the instrument station was moved during measurement. When observations are made using multiple instrument stations, it is important to confirm that the same coordinate reference is maintained at each instrument station and that no unnatural discrepancies appear at the connection points. If data for each instrument station are managed separately, you should also verify during integration that coordinates have not been transformed twice and that local coordinates are not left mixed in.

Checking the coordinate system and reference points before drafting helps stabilize subsequent drawing work. Before tidying the lines and symbols on the drawing, the first step to correctly utilizing total station data is to confirm that the measurement results themselves have the correct positional relationships.

Check for duplicate point names and survey point codes

Next to check is the organization of point names and survey point codes. Measurement results obtained with a total station may include point numbers, point names, survey point codes, and attribute notes. These are important pieces of information when creating drawings, but when measurements are taken in a hurry on site, the same point name may be used in different locations, temporary point names may be left as is, or the method of assigning survey point codes may change partway through.

Before creating the drawing, first check that there are no duplicate point names. Even when point numbers are automatically numbered sequentially, manually entered point names or codes may be duplicated. For example, when measuring boundary points, corners of structures, center points, temporary points, or ends of existing features, repeatedly using the same abbreviations can make it unclear which points should be connected on the drawing. If the person drafting the drawing is the same as the surveyor, they may be able to compensate from memory, but when a different person drafts the drawing or it is reviewed later, ambiguity in point names can lead to major mistakes.

Survey point codes are also important. They are often used to indicate the type of survey point and serve as clues for classifying items such as road edges, side ditches, slope shoulders, toes of slopes, structure corners, stake centers, boundaries, and elevation points. If drawing software is set up to automatically generate lines or assign symbols based on codes, mistakes in entering codes directly affect the drawing output. If a point that should be connected as a road edge has a different code, the line will be interrupted; if points from a different category share the same code, unnecessary lines may be connected.

When checking point names and codes, don't rely solely on the order of field measurements; also verify the positional relationships of the survey points. Even if sequential numbers appear to be naturally ordered, points from another structure may be mixed in. If you operate by connecting points in measurement order, distant points can end up linked, so you need to confirm that the point sequence matches the actual site shape. In particular, when you have measured all the way around a corner of a structure, decide whether to close the start and end points or treat them as an open line—doing so will make drafting smoother.

Be careful about inconsistencies in the notation of point codes. If points with the same meaning are entered in some places in Japanese, in others as abbreviations, and in yet others as numeric codes, it will take time to organize them during the drafting stage. If each site has a standardized code system, check whether the rules are being followed. Even when there is no unified rule, at minimum organize so that the same type of point uses the same notation before drafting to reduce drawing errors.

Also check whether any unnecessary measurement points or trial measurements remain in the result data. Points measured on site to check the instrument or its orientation, points observed by mistake, and old points that were re-measured partway through can get mixed in and appear as unwanted points on the drawings. It is important to decide whether to delete them, hide them, or keep them as reference points. Even if you delete them, saving the original data separately will make it easier to handle if you need to verify it later.

Organizing point names and survey point codes is a process that may seem unremarkable but has a major impact on drawing quality. To produce clean drawings from total station measurements, it is essential to ensure not only that the coordinate values but also the information associated with each point can be read correctly.

Confirm the vertical datum and the handling of instrument height

When converting measurement results from an optical surveying instrument into drawings, if you use elevation information as well as plan position, you must always verify the vertical datum and the handling of the instrument height. Elevation errors are hard to detect when looking only at a plan, but they become major problems when reflected in longitudinal profiles, cross sections, as-built drawings, site development drawings, and elevation control drawings for structures. In particular, when there are multiple measurement days or multiple instrument setups on the same site, carefully check that vertical datums are not mixed.

Height references include elevations based on known benchmarks, heights based on temporary benchmarks on site, reference elevations from design drawings, and arbitrarily set heights. When obtaining heights with a total station, it is important that the instrument height, prism height, the elevation of known points, and the height setting for the backsight are correctly reflected. If even one input is entered incorrectly, the heights of all points can be shifted by a constant amount. Before drafting drawings, it is necessary to verify that the height reference used on site is consistent with the heights in the measured data.

Instrument height and prism height are also easy-to-overlook points. On site, the tripod setup or the prism height may be changed. If those changes are not entered correctly into the total station, errors will occur in the heights of measured points. If you change the prism height during measurements or if observations are made by multiple people, check the records so you can see which height was used for each section. Before drafting the drawings, review the list of heights and check for any ranges that are consistently offset by an unusual amount; this makes it easier to spot input errors.

Even when creating only a plan view, you cannot always afford to completely ignore elevation information. For example, the top of a drainage channel, the pavement surface, the shoulder, the toe of the slope, and the top of a foundation all have meaning in both plan position and elevation. If you will annotate elevation values on the plan or there is a possibility of later developing cross-sections, it is safer to verify the reliability of the elevation data before drafting the drawing. Even on drawings where elevation values are not required, elevation can sometimes provide clues for interpreting the meaning of surveyed points.

Using known reference points is effective for verifying heights. If there are points on site with known heights, compare them with the measured heights to confirm whether the differences fall within an acceptable range for the site and the deliverables. If you can compare multiple points, it becomes easier to determine whether the entire set is uniformly shifted or whether there are localized anomalies. If the whole set is uniformly shifted, suspect the height reference or the instrument height setting; if the shift is localized, check the prism placement, mistaken selection of the measurement target, reflection conditions, errors in point naming, and so on.

In the drafting stage, care must be taken with how heights are rounded. Measurement results include detailed values, but the number of digits displayed on drawings should be adjusted according to their intended use. Showing more digits than necessary makes drawings harder to read, while rounding too much makes them difficult to use for construction management and as-built verification. Decide in advance how many digits to display based on the drawing recipient, internal standards, and the intended on-site use.

Checking the height reference and instrument height is an important procedure that supports the reliability of drawings. When creating drawings using measurement results from a total station, clarifying not only the alignment of horizontal positions but also which vertical datum the heights are based on makes it easier to reduce rework in subsequent stages.

Check for anomalies and outliers in observed values

Before turning the data into drawings, it is also important to check the measurement results for any anomalous values or spurious points. A total station, when properly set up, sighted, and used after verifying conditions, is an instrument that helps achieve high-precision measurements, but depending on site conditions and operating circumstances, unintended points can be included in the measurement data. Causes of anomalous values are varied: the prism position was displaced, a location other than the target was measured, aiming was poor, reflection conditions were bad, people or vehicles entered during measurement, and so on.

An outlier point is a point that is clearly located away from the intended measurement target, or a point that has coordinates or elevations that are unnatural compared to the surrounding point set. If outliers are not checked before creating a plan drawing, the drawing can be greatly distorted when lines are connected, or extra points may be displayed outside the intended area. Especially at sites with a large number of measured points, it is difficult to check each point solely from field memory, so it is effective to check the overall distribution using a coordinate list or a simplified display.

To find outliers, first display all measurement points and check whether any points lie far outside the site boundaries. Next, within the sequence of points measured on the same object, look for points where the position suddenly jumps or where the elevation differs greatly from the surrounding points. If there are abrupt kinks or steps in a point sequence that should normally connect smoothly—such as along a road edge or the edge of a structure—you should reassess the meaning of those measurement points. However, because actual steps or kinks may exist on site, it is important to cross-check with field notes, photos, and the conditions at the time of measurement before judging them as anomalies.

Anomalies in observations can appear not only in planar positions but also in distances and angles. For example, when measuring surrounding points from the same instrument station, if a single point shows an unusually long distance or lies in an unexpected direction, a mix-up of point names or misidentification of the measurement target may be suspected. In measurement data taken after moving the instrument station, checking whether differences appear at the connecting points before and after can sometimes reveal problems in the instrument station setup.

When checking outliers, the important thing is not to delete them immediately. If they are clearly measurement errors, they should be removed, but they may also be important points that indicate the actual geometry of the site. In particular, deformation of existing structures, settlement of pavement surfaces, slope collapses, and breaks near boundaries may, even if they look unnatural compared with the surroundings, reflect actual site conditions. Therefore, before deleting them, it is safest to cross-check with measurement notes, site photographs, and the workers' recollections, and, if necessary, treat them as candidates for re-measurement.

Measurement data may include points measured for verification or provisional points. These are not outliers, but they may be unnecessary on the final drawings. Before drafting the drawings, separating points to be used in the deliverables, points to be retained as references, and points to be excluded will help organize the drawing process. If you draft with unnecessary points left in place, point numbers and annotations increase and the drawings become harder to read.

Measurements from an electronic total station are important primary data obtained on site. However, precisely because they are primary data, it is necessary to check for abnormal or unnecessary data before drafting drawings and to prepare them so they can be used as deliverables. By carefully checking for spurious points and anomalous values, you can prevent unnatural lines and incorrect annotations on the drawings.

Reconcile on-site notes with the meanings of measurement points

When creating drawings from total station survey results, proceeding using only coordinate values and point names can lead to misinterpretation of what the survey points represent. Even points in similar locations require different lines and annotations on the drawing depending on whether they mark a structure corner, the edge of pavement, the inside or outside of a gutter, the top of a slope (shoulder), or the toe of a slope. Therefore, it is important to cross-check the field notes with the surveyed points.

Field notes may record the measurement targets, measurement order, special remarks, areas that were difficult to see, points that need later verification, and points measured provisionally. These are important pieces of information for determining the meaning of points during the drafting stage. In particular, when the person who took the measurements and the person responsible for drawing are different, it becomes difficult to interpret the points without the field notes. Even if measurement data include codes, they cannot fully represent the actual site conditions, so it is necessary to verify them together with notes and photographs.

For example, if you have measurements of the four corners of a structure, you can simply connect the points and depict it as a quadrilateral on a drawing. However, the meaning of the drawing changes depending on whether those points are exterior corners, interior corners, top-edge corners, or ground-level corners. Likewise, when measuring a gutter, the representation varies depending on the measurement location — the outer edge of the cover, the outer face of the gutter body, the inside of the channel, the top-edge elevation, and so on. If you do not confirm the meaning of the measured points before drafting, you may end up with a drawing that is geometrically neat but does not accurately represent the site.

If site photos are available, matching the measurement points to the photos makes verification easier. Photos alone do not provide exact coordinates, but they help in understanding the meaning of the measurement points and the surrounding conditions. Photos taken during measurement that record the point numbers, or photos that show the measurement target more broadly, make it easier to confirm the interpretation of points later. Before drafting drawings, review the measurement data, field notes, photos, and existing drawings together to clarify the meaning of the points.

Also, when cross-checking against the field notes, it is important to verify areas that were not measured. Not all points required to create the drawings may have been measured. Even if you think nothing was overlooked on site, once you start drafting you may find missing points such as those needed to close lines, to indicate level changes, to determine boundaries, or to show the depth of structures. By cross-checking the meaning of the measured points and confirming that all information necessary for drafting is present, you can make a quicker decision about whether re-measurement is needed.

When there are uncertainties, it is important not to produce drawings based on guesses. Even if the site shape appears simple, a single line on the drawing can affect construction decisions and quantity calculations. If you draw lines while the meaning of measurement points is ambiguous, you may end up with drawings that do not match the site, requiring rechecks or revisions. It is safer to leave unclear points as unknowns, confirm them with the surveyor, or, if necessary, recheck them on site.

The measurement results from a total station may be well organized as numbers, but if those numbers are not correctly understood in terms of what they represent, their value as drawings is diminished. The process of reconciling field notes with the meanings of measured points is an important bridge for converting measurement data from a mere collection of coordinates into drawing information that represents the site.

Verify the connections of lines necessary for drafting

When converting measurement results into drawings, it is important to confirm in advance which points should be connected by lines. Points acquired with a total station exist individually as coordinates, but on drawings they are transformed into lines and shapes such as road edges, structure outlines, gutters, boundary lines, slope shoulders, slope toes, and centerlines. If these line connections are mistaken, it will affect the interpretation of the entire drawing and construction decisions.

To check the connectivity of lines, first group the points by measurement target. Organize points measured on the same structure, points measured at the same road edge, points on the same boundary line, points that indicate the same change in elevation, and so on, and confirm in which order each group should be connected. It is clearer if point numbers are arranged in measurement order, but on site it is sometimes not possible to measure in sequence due to efficiency or line-of-sight issues. Therefore, rather than automatically connecting lines based only on point numbers, you need to verify them while referring to positional relationships and site notes.

Pay particular attention to the difference between lines that should be closed and those that should remain open. Building outlines, foundation outlines, inspection chambers, and the contours of structures are often represented as closed shapes, whereas road edges, side ditches, slope shoulders, slope toes, channel centerlines, and temporary lines may be treated as open lines. If a line that should be closed is left open, the figure becomes incomplete; conversely, forcibly closing a line that should remain open will create lines on the drawing that do not exist on site. Before drafting drawings, it is important to confirm the nature of each line.

Also check the types of lines. Lines represented by solid lines, dashed lines, centerlines, lines that distinguish existing and new work, lines treated as reference lines, etc.—the representation changes depending on the purpose of the drawing. Because measurement results alone often do not allow the line type to be determined, it is necessary to organize them according to the intended use of the deliverable drawing. For drawings used to verify as-built conditions, the difference between the measured lines and the design lines must be made easy to understand. For drawings used to check a site, the positional relationships of boundaries and structures must be easy to read.

Also, when multiple sets of points are close to one another, be careful not to connect the wrong lines. For example, the left and right sides of a gutter, the upper and lower edges of a road, the slope shoulder and toe, and the top and bottom of a retaining wall can lie close together on a plan. If you connect them incorrectly, the lines may look plausible on the drawing but will not match the actual shape. Use elevation information and field notes to confirm which sets of points belong to the same element.

When checking line connectivity, consider not only the appearance after drafting but also how it will be used in downstream processes. For drawings used for area calculations, it is important that they are correctly constructed as closed figures. When used for quantity takeoff, the lines needed to calculate lengths, widths, and areas must be properly organized. When used for construction verification, it is essential that the relationship between design lines and measured lines is clearly expressed.

The measurement points from a total station only take on meaning as lines and shapes once they are drawn. By checking the connectivity of the lines before plotting, you can reduce drafting errors and prepare the drawings so they are easy to use as final deliverables.

Confirm the accuracy and notation appropriate for the intended use of the deliverable drawings

Before converting measurement results from a total station into drawings, you need to confirm that the deliverable drawings have the accuracy and presentation appropriate for their intended use. Even if the measurement data are correct, drawings that are too detailed for their purpose or, conversely, lack sufficient information will be difficult to use in practice. Drawings should not merely depict the site; it is important to organize them with consideration of who will use them and for what purpose.

First, clarify the purpose of the drawings. The information required differs depending on whether the drawing is for confirming current conditions, for use in construction planning, for use in as-built management, for explaining to stakeholders, or as a deliverable for submission. For existing-condition drawings, it is important that the positional relationships of existing structures and the terrain are easy to understand. For as-built drawings, the relationships between design values and measured values, dimensions, elevations, and the locations of control points are important. For explanatory drawings, avoid packing in too much specialist information and use easily readable expressions.

When checking accuracy, you need to consider not only measurement accuracy but also the display precision on the drawing. Even if a total station obtains detailed figures, depending on the drawing scale and purpose, it may not be necessary to show all digits. Conversely, when used as a management/control drawing, omitting required digits can hinder decision-making. The number of digits displayed for coordinate values, elevations, distances, and dimensions should be standardized to match the drawing’s purpose.

The scale of the drawing is also important. If you display measurement results as-is, points and annotations can become clustered and hard to read. In particular, around structures, in urban areas, or within narrow construction zones, measurement points tend to concentrate, and showing them all on the same drawing can result in information overload. In such cases, it is necessary to organize the information with readability in mind—for example, separate overall and detail drawings, adjust annotation positions, or hide unnecessary reference points.

Also check how lines and text are represented. If existing elements, new elements, design lines, surveyed lines, centerlines, boundary lines, reference lines, etc. are shown in the same way, it will be difficult for people viewing the drawings to tell them apart. Organize colors, line types, line widths, and how annotations are added so that differences in information are clear on the drawings. However, because making representations too complex can actually make them harder to read, it is important to limit them to the necessary categories.

In the deliverable drawings, the relationship between the measurement results and the design information is also checked. When overlaying the measured line and the design line, the existence of an offset itself is important information about site conditions. However, treating offsets caused by differences in coordinate systems or drafting errors as site discrepancies can lead to incorrect judgments. Before preparing the drawings, it is necessary to verify that the measurement data and the design data are aligned to the same reference, and only then express the differences.

When submitting drawings as deliverables, also check whether the drawing contains the necessary basic information. Organize the information that someone viewing the drawing needs to understand its contents, such as the drawing title, measurement date, scale, orientation, reference points, measurement range, legend, and notes. Even for simple drawings used on site, make them so that when you look back later you can tell what the drawing is, which increases their value as records.

The purpose of converting measurement results from a total station into drawings is to present accurate data in a clear, usable form. Rather than focusing solely on measurement accuracy, checking the drawing’s intended use, readability, and consistency of presentation makes it easier to produce deliverable drawings that are useful in practice.

Workflow for Preparing Total Station Measurement Results Before Drafting Drawings

As confirmed so far, before plotting the measurement results of an optical total station, it is necessary to organize multiple aspects such as the coordinate system, reference points, point names, survey point codes, vertical datum, abnormal values, field notes, line connectivity, and the intended use of the drawings. Because checking these items ad hoc often leads to omissions, in practice it stabilizes the work to establish a fixed workflow.

First, when you receive measurement data, save the original data as-is. Even if you modify point names or organize out unnecessary points for drafting, keeping the original data makes it possible to revert when later confirmation is needed. Survey data are the primary records from the field, and it is preferable to manage them separately from data processed for drawing. Clearly distinguishing raw data, cleaned data, and drawing data also makes it easier to track revision history.

Next, verify the coordinate system and reference points. Confirm the known points used, the backsight points, the instrument point(s), and the measurement range, and check whether the assumptions for overlaying with existing drawings and design data are consistent. If any overall positional shifts or orientation differences are found at this stage, determine the cause before proceeding with drafting. If you start drawing lines while coordinate alignment is still unclear, you may need to revise the entire drawing later, so this should be settled first.

After that, organize the point names and measurement point codes. Check for duplicates, inconsistent notations, unnecessary points, provisional points, and possible missing measurements, and clarify which points will be used for drafting. If the meaning of a point is unclear, cross-check with field notes and photos. If the surveyor and the drafter are different people, align your understanding at this stage to help prevent incorrect line connections and annotation errors.

When creating drawings that use elevation information, verify the consistency among the height datum, instrument height, prism height, and the elevations of known control points. Because elevation anomalies can be difficult to detect after drafting, review elevation lists and cross-section directions to check for any anomalous values. Even when producing only plan views, elevation can provide clues for interpreting what a point represents, so it is safer not to ignore it completely.

Next, check for anomalous values and outliers. Identify points that fall outside the site area, points whose elevation differs greatly from their surroundings, and points that cause an unnatural bend in the point sequence, and determine whether they are measurement errors or actual site features. Clean up unnecessary points, and record any points you cannot decide on as pending so they are easier to review later.

Finally, organize the connectivity of the lines and the drawing representation. Confirm which points to connect, whether lines are closed or open, how to distinguish existing from new elements, and how to represent design lines versus measured (as-built) lines, then express them in a way that suits the intended use of the deliverable drawings. Drafting the drawings is not merely a conversion task but the process of organizing measurement data into information that can be used in practice. It is important to be mindful of both the correctness of the measurement results and the clarity of the drawings.

The total station is an important surveying instrument for determining positions and elevations on site. However, when turning measurement results into drawings, checking and organizing the data is essential. By making seven pre-drawing checks a habit, you can reduce drafting mistakes and rework and make it easier to produce deliverable drawings that are easy to use in the field.