RTK QA/QC Template: A Reproducible Checklist for Deliverables

Table of Contents

• What is QA/QC in RTK surveying? Its importance and challenges

• 1. Pre-survey preparation: instrument calibration and settings verification

• 2. Verification of control point coordinates and coordinate systems

• 3. Observation planning and environmental condition checks

• 4. Real-time checks and error countermeasures during surveying

• 5. Accuracy validation by redundant observations

• 6. Data processing and quality analysis

• 7. Final checks and documentation of deliverables

• Conclusion: Leveraging new LRTK technology to support reproducibility

• FAQ

What is QA/QC in RTK surveying? Its importance and challenges

RTK (Real-Time Kinematic) surveying is an advanced technique that uses satellite positioning to achieve high accuracy on the order of a few centimeters (a few in). However, no matter how advanced the technology, its true value cannot be realized without proper quality management. This is where QA/QC becomes important. QA (Quality Assurance) refers to the systems and plans put in place to ensure quality throughout the work process, while QC (Quality Control) means inspecting and verifying that the actual deliverables meet the required standards.

QA in surveying includes pre-work efforts such as planning the survey and calibrating and inspecting equipment. QC, on the other hand, is the stage after surveying in which data accuracy is verified and errors are checked to ensure the quality of the deliverables. In RTK surveying, a single mistake in setting the base station coordinates can shift all coordinates measured by the rover, and poor radio conditions can introduce errors into the data. To prevent such risks and obtain reproducible survey results (i.e., results that anyone would obtain the same), meticulous QA/QC is indispensable.

In practice, however, fieldwork is often rushed and the attitude of "just measure and deliver" is common. In such cases, positional shifts or missing data may be discovered later, leading to rework and loss of trust. This article explains RTK QA/QC points in a checklist format for early- to mid-level survey technicians. It organizes steps from pre-survey preparation to on-site cautions during observation, data verification, and deliverable checks. Using this template will help reduce variability in survey quality and enable you to consistently deliver highly reliable results.

1. Pre-survey preparation: instrument calibration and settings verification

Before starting the actual survey, thorough preparation of equipment and settings is required. It is often said that proper preparation determines 80% of quality, so pre-checks are crucial. Below are the main items to confirm before beginning surveying.

• GNSS equipment and controller status check: Check that the RTK-GNSS receivers, antennas, and controller devices to be used are functioning normally. Update firmware and software to the latest versions, and reset or reconfigure any lingering previous settings as necessary. Also confirm that batteries are fully charged and prepare spare power sources.

• Instrument calibration and inspection: GNSS equipment does not generally require periodic calibration like total stations, but if using a pole with an inclinometer, calibrate the electronic bubble level. Also check that monopods and tripods stand straight and that bubble levels indicate true horizontal.

• Communications and correction data preparation: If using network RTK, test Ntrip connection settings (ID, password, mountpoint, etc.) to ensure they are correct. Check SIM cards and mobile routers for communication status, and if a cellular dead zone is expected, consider alternatives such as CLAS (QZSS augmentation) in advance. If using your own base station, match the radio frequency and ID settings with the rover and perform communication tests.

• Positioning mode and recording settings: If a specific positioning mode is required for the survey (e.g., record only fixed solutions), set this on the controller. If possible, enable options to record raw data (RINEX) or satellite observation logs. This allows verification through post-processing if needed.

• Check required equipment: In addition to GNSS receivers and antennas, prepare prism poles, monopods/tripods, spare batteries, and surveying accessories (writing tools, marking supplies, etc.). Reconfirm the complete equipment list against a checklist to avoid unexpected shortages on site.

Careful completion of these preparatory tasks prevents on-site issues such as “the equipment won’t power on” or “we must remeasure due to a setting error.” As a QA step, this process solidifies the foundation that determines surveying quality.

2. Verification of control point coordinates and coordinate systems

In RTK surveying, the accurate setting of the control point (base station) coordinates is extremely important. If the control point coordinates are incorrect, all coordinates obtained by the rover will be offset by the same amount. Confirm the following points in advance.

• Use and validation of known points: If public survey control points (benchmarks, triangulation stations) exist at the site, consider using their coordinate values. If possible, place the control station on a known point and input the known coordinates. If no known point exists, investigate nearby electronic reference stations or the coordinate system information for virtual reference stations (VRS) to understand the local datum. If previous survey data from the same site exist, reference them to check consistency of control points.

• Presence of a local coordinate system: If a construction coordinate system (local coordinate system) is used on-site, obtain its definition and parameters in advance. For example, if a specific Japan Plane Rectangular Coordinate System zone or a custom origin and orientation are defined, calculate the base station coordinates accordingly. If necessary, measure azimuths between known points in the field with a total station and compare with GNSS results to verify conversion accuracy to the local coordinate system.

• Verification of height datum: GNSS provides ellipsoidal heights, so confirm whether conversion to orthometric height is required. If you use a geoid model from the Geospatial Information Authority of Japan (e.g., JSI-GEOID2020) to convert to orthometric heights, record the model name and ensure the same model is used consistently. This information is important for reproducing results.

• Antenna height / instrument height input: Double-check that antenna heights for the base station and rovers are entered correctly. Mistakes in antenna height (height from the antenna reference point to the ground or measured point) are a common error. Reconfirm values before going to the field and monitor pole extension and fastening during surveying.

Correctly setting and verifying control point coordinates and coordinate systems ensures not only relative accuracy between surveyed points but also absolute accuracy. When performing QC comparisons with other data, matching datums makes cross-checking straightforward. Always be conscious of whether the control is stable; if necessary, perform a test measurement against a known point to check for errors.

3. Observation planning and environmental condition checks

To obtain stable positioning accuracy on site, both a survey plan and environmental checks are essential. Rather than going to the field and measuring at random, plan using the following points.

• Consider satellite geometry and time of day: GNSS satellite geometry changes over time. If you can check satellite visibility forecasts or PDOP predictions for the planned survey date, choose time windows with favorable conditions. This is especially important in valleys or urban areas with limited sky view, where satellite positions can strongly affect accuracy.

• Pre-check the field environment: Visit the site beforehand to confirm whether the sky is sufficiently open. Tall buildings, cranes, and dense trees can block satellite signals or cause multipath reflections. Choose base station locations and primary survey points with as clear a view of the sky as possible. If measuring under unavoidable poor conditions, prepare contingency plans such as extending observation times to average, or supplementing with alternative methods.

• Number of points and redundant observation plan: Prepare a list of points to be measured and an efficient route. Include plans for redundant observations (re-measuring the same point) as discussed later. For example, measure the same control point at the start and end of the day, or observe critical benchmarks more than once at different times. This secures data for later quality verification.

• Required accuracy and observation method selection: Identify the required accuracy on site (e.g., horizontal ○ cm, vertical ○ cm) and plan observation methods to meet it. For example, if vertical accuracy is strict, consider supplementing RTK with leveling or conducting observations for a minimum duration and averaging. Using multiple rovers simultaneously for cross-checks can also be effective for important tasks.

Planning from a QA perspective about how to reliably secure accuracy before arriving at the site will make fieldwork smoother and reduce the risk of problems being found during QC.

4. Real-time checks and error countermeasures during surveying

During actual RTK surveying, it is important not to neglect QC-type checks that can be done on the spot. By performing real-time error checks and addressing issues immediately, you can avoid rework. Below are points to watch during surveying.

• Maintain and monitor FIX solutions: Always confirm on the controller or app that your positioning solution is “FIX (fixed solution).” FIX indicates centimeter-level accuracy; if the display shows “FLOAT” or “DGPS,” accuracy is lower. If FIX cannot be obtained during measurement, hold off measuring that point, try changing the antenna position, check communication with the base station, or wait and retry.

• Check satellite count and PDOP: For each point, check the number of GNSS satellites received and the PDOP (Position Dilution of Precision) value. If the satellite count is extremely low (4–5 barely) or PDOP is high, the point’s accuracy is unstable. In such cases, consider extending observation time or waiting for improved conditions before re-measuring.

• Monitor radio and communication status: If receiving corrections via radio, monitor signal status; if using Ntrip, check mobile data connectivity. Interrupted or delayed communication prevents proper correction data from being received and affects positioning. As needed, raise the base station antenna, add a repeater, or move to a location with better cellular reception to perform measurements.

• Detect abnormal values: Watch real-time measurement values for obvious anomalies (e.g., coordinates suddenly jumping by tens of centimeters, or unnatural spatial relationships compared to adjacent points). If suspected, measure the same point for several seconds and use an average, or remeasure the point to avoid including abnormal values.

• Record field notes: If you notice anything or encounter trouble during surveying, record it in a field note. Examples: “FIX momentarily lost at point ○○,” “point △△ on soft ground—possible pole settlement.” These notes are useful when reviewing data later. They may not be included in final deliverables but should be kept internally for QC analysis.

Thorough real-time QC prevents finding unusable data only after returning to the office. In the field, maintain a supervisory mindset alongside surveying—if anything feels off, stop, isolate the cause, and address it. This cautious approach leads to final quality assurance.

5. Accuracy validation by redundant observations

An effective QC method for field data is accuracy validation through redundant observations. Measuring the same point multiple times or using independent methods for some points helps confirm data reliability.

• Start and end point comparison: Measure a common point (for example, a known point near the base station or a temporary benchmark) at the start and end of the day, and compare the coordinates. Checking for differences between the start and end measurements lets you detect any accumulated systematic error during the day. If a noticeable difference appears, suspect shifts in the base station coordinates and consider re-measurement or correction.

• Re-measure critical points: Re-measure particularly important points (control points or design-critical points) at least twice with time separation. If the two measurements fall within an acceptable range (for example, within ±2 cm (±0.8 in) horizontally and ±3 cm (±1.2 in) vertically), consider them acceptable. If differences are large, perform additional measurements or verify with an alternate method (e.g., total station).

• Cross-check observations: If possible, cross-check using a method other than RTK. For example, observe a few points with a total station and compare with GNSS results, or use a different GNSS receiver or base station. For public surveys or critical control surveys, combining GNSS with total station or leveling for mutual verification is recommended.

• Statistical accuracy evaluation: When you have redundant observation data, calculate statistics (mean error, standard deviation, etc.) for the differences. Repeated measurements of the same point allow you to evaluate precision from the spread; if known control points exist, analyze residuals to assess accuracy. Summarize these results in a quality report or accuracy verification sheet for inclusion with deliverables where appropriate.

Redundant observations provide corroboration for survey data. Although it increases effort, if data come into question you can explain “this data was verified as having accuracy of XX based on these checks,” which enhances trust in your work.

6. Data processing and quality analysis

After field observations are complete, return to the office for data processing and quality analysis. Here you organize the collected data, apply necessary corrections or analyses, and evaluate quality.

First, export point data from RTK devices or apps and plot the coordinate list on CAD drawings to get an overall view. At this stage, confirm that the coordinate system is as expected and that there are no unnatural offsets or jumps in point placement. Check whether distances between adjacent points are reasonable and whether the data aligns with design drawings or existing maps.

If you collected raw data (RINEX) or observation logs in the field, performing simple post-processing with GNSS analysis software is useful. For example, process each point’s observation file together with the base station data and compare the post-processed solution with the RTK result to verify correctness. For distant points or those measured under poor signal conditions, post-processing may improve accuracy.

For redundant observations, compare results and summarize the error margins in a table. Use spreadsheet software to compute residuals and produce histograms and statistics for an objective evaluation of data precision. For example, you might report “RMSE of horizontal position for five checkpoints is 1.8 cm (0.7 in), RMSE of vertical is 2.5 cm (1.0 in).”

When combining RTK data with other datasets such as point clouds or photogrammetric 3D models, also verify alignment accuracy. Use RTK-derived GCPs (Ground Control Points) or checkpoints to align point cloud models and check for offsets as part of quality analysis.

After these processing and analyses, determine whether the required accuracy criteria are met. If some data do not meet standards, consider additional surveying or exclude problematic data. The numerical results of quality analysis are easy to communicate to stakeholders and serve as feedback for improving future work.

7. Final checks and documentation of deliverables

Finally, perform a final check of deliverables to be submitted to the client or purchaser. Confirm not only data formatting but also that quality-related information is properly reflected.

• Formatting of deliverable data: Confirm that coordinate lists and drawing files to be delivered conform to the specified formats and file types. Double-check point numbering, naming, and unit mistakes (e.g., confusion between meters and feet). Clearly annotate the coordinate system and datum, for example “JGD2011 (Heisei 23) Zone ○,” to avoid recipient misunderstanding.

• Inclusion of metadata and notes: On drawings and reports, include metadata such as survey date and time, equipment used, surveying method (RTK), control point information, coordinate system, and any transformation parameters if applicable. This makes results traceable when the data are reused or reviewed by third parties.

• Attach quality verification results: Where possible, attach the accuracy verification results performed earlier. Examples include residual tables for checkpoints, error statistics, and comments on survey accuracy. For public surveys, submission of an accuracy control sheet or quality certificate may be required; even in private work, providing such information reassures recipients. Visual materials such as difference plots or alignment evaluation with point clouds are particularly helpful.

• Ensure reproducibility of data: From the perspective of reproducibility, deliverables should allow future reproduction and verification. For example, retain and, if appropriate, share raw GNSS observation data (RINEX), base station coordinates, the name of the geoid model used, and the coordinate transformation parameters (origin and orientation for plane rectangular coordinates). Keep these records internally and share with the client if needed. This ensures that if the datum changes in later years or verification is required, results can be reproduced from the original data and long-term trust in the survey results is maintained.

After these final checks and documentation steps, the deliverables can be handed over. Thoroughly organizing and providing quality information demonstrates professionalism as a surveyor and serves as a preventive measure against disputes. It also helps recipients correctly understand how to use the data and facilitates smooth secondary use and construction implementation.

Conclusion: Leveraging new LRTK technology to support reproducibility

So far we have detailed the QA/QC points for RTK surveying in a checklist format. You should now understand that using high-accuracy RTK in the field requires substantial preparation and careful checks. Although these procedures increase the number of tasks, they dramatically improve the reliability of the survey data obtained.

That said, some may feel that performing all these checks every time is burdensome. In such cases, consider adopting modern simplified surveying systems. For example, the LRTK series is an innovative positioning system that combines RTK-GNSS and a smartphone, designed so that even a single operator without specialized knowledge can perform centimeter-level measurements—cm level accuracy (half-inch accuracy). By incorporating LRTK, some calibration and data synchronization tasks that previously required experience and effort can be automated, significantly reducing the QA/QC burden in the field. Also, data collected can be synchronized to the cloud in real time, allowing office staff to monitor field survey results remotely.

Using simplified LRTK surveying allows you to enjoy high accuracy while reducing cumbersome tasks. For details on the LRTK series, please see the LRTK official site: https://www.lrtk.lefixea.com. Even beginners concerned about quality control can follow the system’s guidance to obtain reproducible results. By combining new technology with proper QA/QC practices, you can continue stable surveying operations. Balance productivity and quality using RTK surveying together with innovative tools.

FAQ

Q: What is the difference between QA and QC? What do they refer to in surveying? A: QA (Quality Assurance) refers to measures taken to ensure quality throughout the surveying process, including pre-survey preparation, development of procedures, and establishment of rules. QC (Quality Control) refers to activities that verify the quality of final deliverables, such as inspecting and confirming that obtained coordinate values and drawings meet required accuracy. In short, QA is “preventive measures to get good results,” while QC is “inspections to check whether the results are good.” Both are essential in surveying; only when both are in place can highly reliable deliverables be produced.

Q: What level of accuracy can be expected with RTK surveying, and how should it be verified? A: With typical dual-frequency GNSS RTK surveying, horizontal errors of approximately 2–3 cm (0.8–1.2 in) and vertical errors of approximately 3–5 cm (1.2–2.0 in) can be expected under good conditions. This is far more accurate than standalone positioning (errors of several meters (several ft)). To verify accuracy, compare with known points or analyze differences from redundant observations as described in this article. Displayed estimated accuracy on the controller (e.g., horizontal ±1 cm, vertical ±2 cm) is a theoretical value, so always verify with actual measurements.

Q: Won’t thorough QA/QC in the field extend work time? A: Indeed, additional checks and redundant observations will increase field and post-processing time. However, this effort prevents re-surveys and adverse effects on design or construction, so it is efficient overall. The key is to incorporate QA/QC into workflows so it becomes routine. For example, divide check items among team members for mutual verification or use standardized check sheets to equalize the burden. Tools like LRTK can automatically collect inspection data, so actively using such tools is recommended.

Q: If an error in survey deliverables is found after delivery, what should be done? A: First, identify the error and analyze the cause. Responses differ depending on whether the issue is a coordinate system mix-up, a simple transcription error, or an observational error. Once the cause is identified, promptly perform re-surveying or data correction and submit a revised version. Also review why the QA/QC process did not catch the error and improve checklists or procedures accordingly. It is important to explain the situation sincerely to the client and present measures to prevent recurrence. Regular data backups and documented procedures help you respond calmly when problems occur.

Q: If we adopt the latest surveying technology, will QA/QC become unnecessary? A: Introducing the latest technology (e.g., smart GNSS devices or automation software) can reduce human errors and omissions, but it does not eliminate the need for QA/QC. No matter how good the equipment, misuse can still cause errors, and humans are ultimately responsible for evaluating system outputs. Consider new technology as supporting QA/QC: use auto-recorded logs for quality analysis, rely on real-time alerts for anomaly detection, and so on. Combining technology with human expertise will achieve even higher reliability in surveying.