RTK Offset Settings Basics and On-Site Tips from LRTK — Reassuring for Surveying Beginners

Table of Contents

• What RTK offset settings are

• Basics of RTK offset settings

• On-site points to keep in mind

• Recommendation: simple surveying with LRTK

• FAQ

In construction sites and the surveying world, various measures are taken to determine positions with high accuracy. Among these, the concept of an “offset” can be somewhat hard to grasp for beginners and may cause anxiety. Especially with RTK (Real Time Kinematic) positioning, which has become widespread in recent years, the procedure called RTK offset setting is a key to accurate positioning. However, the many technical terms and configuration items can confuse those with limited experience.

This article explains the basics of “RTK offset setting” and practical on-site tips in an easy-to-understand way so that surveying beginners can perform RTK surveying with confidence. We start from the basics—what RTK is and why an offset is necessary—then explain concrete configuration methods and tips to avoid mistakes on site. Finally, we introduce a modern solution for simplifying complex settings: simple surveying with LRTK. Please read to the end and apply these tips on site.

What RTK offset settings are

First, let’s clarify the meaning of the term “RTK offset setting.” RTK stands for Real Time Kinematic and is a positioning technique that uses GNSS (satellite positioning) with real-time error correction to determine positions with extremely high accuracy on the order of a few centimeters. By communicating correction information from a base station to a rover receiver, RTK cancels GPS positioning errors on site and immediately acquires high-precision coordinates. Tasks that previously took several people and a long time are increasingly becoming manageable by a single operator using RTK.

So what is an “offset”? In general, an offset means a position shifted from a reference position. In surveying, for example, an “offset stake” may refer to a stake driven a fixed distance away from a design line—i.e., a position translated parallel from a reference. But the meaning of offset setting in RTK is slightly different. In RTK surveying, a GNSS antenna is mounted on a pole or surveying instrument to measure a point on the ground. Because the antenna is located above the ground surface, you must correct for that height to obtain the true ground coordinates. Simply put, RTK offset setting is the process of measuring how many meters the antenna is floating above the ground and entering that value into the device so the positioning result reflects the ground point.

For example, consider surveying by mounting a GNSS receiver on a pole whose tip is placed at the point you want to measure. If the height from the ground to the center of the receiver antenna is 1.5 m (4.9 ft), without correction you would only obtain the antenna’s coordinates and the measured ground point would have a vertical offset of 1.5 m (4.9 ft). To eliminate this offset, RTK surveying requires setting the antenna height (offset amount) beforehand. If you input “antenna height = 1.5 m (4.9 ft)” in the surveying app or receiver settings, the system automatically subtracts 1.5 m (4.9 ft) from the measured coordinates to calculate the ground point coordinates. This way, the final coordinates represent the ground point directly beneath the antenna (the position of the pole tip).

In short, RTK offset setting means entering in the device the height (and sometimes horizontal distance) between the GNSS device and the measurement point, so the system can apply a correction. If this setting is not performed correctly, even highly precise RTK measurements will produce coordinates that are offset from the true position. Vertical errors are particularly hard to notice, so offset setting is a fundamental and crucial part of RTK surveying.

Basics of RTK offset settings

Now let’s look at the basic procedures for offset settings in RTK. Here are step-by-step points beginners should understand.

1. Measure the height to the antenna accurately: First, set a pole or monopod at the ground point you want to measure (a control point or any survey point), and mount the GNSS receiver or smartphone-based RTK antenna on it. Next, measure the vertical distance from the ground point to the antenna reference point. Typically, with the pole tip (shoe) touching the ground, measure from that point to the bottom surface of the receiver using a tape measure or a graduated pole. In many devices, if you input the height to the antenna bottom, the internal antenna offset (difference to the phase center) is compensated automatically according to the model. Therefore, on site it is sufficient to measure the vertical distance from the ground to the antenna bottom.

2. Enter the value according to the measurement method: Once you have measured the antenna height, enter that number in the RTK receiver or surveying app settings. The input field may be labeled “antenna height” or “offset value.” The unit is generally meters, so for example 150 cm (59.1 in) would be written as 1.500 m (4.921 ft) in decimal meter notation (some apps may allow cm input). Also, when there is a choice of measurement type, select “perpendicular distance (vertical)” as usual. Slant distances measured diagonally are prone to error, so always measure and input the vertical distance directly beneath the antenna.

3. Behavior after setting the offset: After you set the offset value, the RTK device subtracts that value (in the vertical direction, for height) from the obtained GNSS coordinates and outputs the corrected coordinates. As a result, the recorded coordinates represent the ground point under the antenna rather than the antenna position. Beginners may worry, “Is it really enough to just enter the height into the machine?”—but if the value is entered correctly, altitude correction is performed automatically. Conversely, if you enter the wrong value, the incorrect coordinates will be recorded, so be careful.

4. Input errors and their impact: The most critical issue with offset settings is input mistakes. For example, suppose the true antenna height is 1.8 m (5.9 ft) but you accidentally leave the setting at “0 m (0 ft).” In that case, a vertical error of 1.8 m (5.9 ft) will occur and the measured point’s elevation will be recorded 1.8 m (5.9 ft) lower than actual. Such errors are hard to notice and may only be discovered later when comparing with drawings—“the elevations are all off.” Even if the antenna height is entered correctly, be careful not to measure with a tilted pole. If the pole is tilted, a horizontal offset will arise between the antenna and the ground point, which affects precise positioning (as discussed later, if your device lacks tilt compensation, keep the pole as vertical as possible).

5. Managing offset values according to the situation: Whenever you change the pole or device setup, review and update the offset value. A common mistake is to change the length of a telescoping pole or swap adapters but continue measuring with the old offset setting. For instance, you initially set 1.5 m (4.9 ft) but later extend the pole to 1.8 m (5.9 ft) and forget to update the setting—this creates a 0.3 m (1.0 ft) error. Under time pressure on site, it’s easy to forget, but remember device setup change = update offset setting, and make a habit of keeping values up to date.

That covers the basics of RTK offset settings. In summary: accurately measure and input the antenna height and keep it updated, and RTK will provide highly accurate results including altitude.

On-site points to keep in mind

Even if you understand the theory, unexpected errors can occur in the field. Especially for beginners performing RTK surveying for the first time, nervousness or a hurried work pace can cause skipped steps. Here are several practical tips to ensure offset settings are done reliably and to prevent failures on site.

• Measurement posture check before measuring: When setting the pole or monopod with the GNSS receiver, keep it strictly vertical at the measurement point. If a bubble level is included, check that the bubble is centered each time. A tilted pole causes horizontal displacement between the antenna and the measured point, preventing accurate positioning. Pay special attention on windy days or at unstable footing.

• Proper placement on the measurement point: Verify that the pole tip (shoe) is actually on the point you want to measure. Though obvious, double-check that the pole is correctly placed on the mark and that it hasn’t moved during work. For control points marked by stakes or nails, ensure the tip is firmly on the mark. Even a slight displacement causes positional error regardless of offset settings.

• Confirm offset setting values: Before starting positioning, recheck the antenna height value entered in the app or receiver. This is especially important if you changed the pole length during setup or swapped equipment while moving. Don’t assume “it’s fine because I set it earlier”—make it a routine to confirm the current setting before starting work. If possible, do a test measurement and check whether the resulting elevation is reasonable.

• Follow manufacturer-recommended procedures: If you use special mounting methods, such as attaching a smartphone to the side of a pole with an L-shaped adapter, follow the device-specific offset procedure. If the manual instructs you to input a horizontal offset (e.g., “in addition to antenna height, input horizontal offset of X cm”), be sure to do so. Non-standard mounting often requires unique corrections.

• Verification with known points: If possible, measure a known coordinate point on site (a point whose correct coordinates are already known) using RTK and compare the results. If the known point yields correct values, you have confirmation that the system and offset settings are working properly. If no known point is available, at least measure important points twice or more and compare results to detect anomalies early.

Following these points will prevent most basic errors related to RTK offset settings. In particular, incorporate “keep the pole vertical” and “confirm setting values” into your routine for each measurement point. Small attention to these items will greatly reduce human error on site.

Recommendation: simple surveying with LRTK

So far we’ve covered the basics of RTK offset settings and on-site precautions. While RTK surveying provides centimeter-level accuracy, making full use of that accuracy requires careful device settings and site checks, which can be a high barrier for beginners. To meet the need for “using RTK surveying more easily,” there is a solution: simple surveying with LRTK.

The LRTK series is a smartphone-based RTK positioning system provided by Lefixea, developed so that anyone can perform centimeter-class surveying easily. By attaching a dedicated compact high-performance GNSS receiver to a smartphone or tablet and linking to cloud correction data services, LRTK enables high-precision positioning without worrying about complex settings. Tasks that traditionally troubled users—such as configuring coordinate systems or managing base stations—are simplified because LRTK uses public reference station data and satellite augmentation services over the network (for example, Japan’s QZSS CLAS), so you don’t need to perform coordinate transformations or set up dedicated base stations on site. Just take the device and start positioning in the app to automatically begin high-accuracy positioning in the correct coordinate system.

Also, the positioning status and accuracy information are displayed intuitively on the smartphone screen, so beginners can immediately understand whether the system is functioning correctly. It’s easy to see whether a fixed solution (Fix) has been obtained, how many satellites are being tracked, and other precision indicators, making it easier to notice mistakes. Regarding offset settings, when using dedicated poles or monopods you can simply select a preset antenna height, minimizing manual input errors. Positioning data is automatically backed up to the cloud, so you don’t have to worry about losing or forgetting data. Since measured information is shared instantly in the cloud, you can review results in the office right after measuring and receive feedback.

Furthermore, the LRTK series is pocket-sized yet offers performance comparable to expensive surveying equipment. Without large dedicated apparatus or many personnel, individual site personnel can conduct surveys with a smartphone in hand. This eliminates concerns about borrowing costly instruments or scheduling and enables immediate measurements when needed, improving site speed. LRTK, aiming to be a “one-per-person universal surveying device,” has already been adopted in domestic construction sites and local government work due to its ease and reliability.

If you are uneasy about RTK settings or equipment handling, consider adopting such a modern simple surveying system. By using LRTK, non-specialists can follow correct procedures and drastically reduce human error. With the convenience of smartphone operation and the assurance of cloud integration, surveying productivity and quality will improve significantly. For more information, please see the [LRTK official site](https://www.lrtk.lefixea.com/). LRTK can transform your field surveying style and be a reliable partner that allows beginners to work with confidence.

FAQ

Q: What kind of technology is RTK? A: RTK (Real Time Kinematic) is a technology that uses two GNSS receivers—a base station and a rover—to perform real-time correction of satellite positioning errors. By receiving correction information from the base station, the rover reduces positioning errors that would normally be several meters down to a few centimeters. RTK is widely used at construction sites for immediate high-precision surveying and stakeout.

Q: Why is offset setting necessary in RTK surveying? A: Because the GNSS receiver’s antenna is located above the ground, you measure the antenna position, not the ground point. Therefore, you must set the antenna height (offset) beforehand so the system can correct the measured coordinates. If you neglect this, the coordinates will always include the antenna’s vertical offset and won’t represent accurate ground positions. Since vertical discrepancies are hard to notice on site, always perform offset setting in RTK surveying to obtain correct ground-surface coordinates.

Q: How should I measure the antenna height offset? A: Basically, measure the vertical distance from the ground point to the antenna reference. Specifically, with the pole tip on the measurement point, measure from that location to the bottom surface of the GNSS antenna using a tape or the graduations on the pole. Many receivers accept the antenna-bottom height and internally apply the proper correction, so input that value as the antenna height. If you use a fixed-length dedicated pole, you may simply use the catalog length or select a preset in the app.

Q: What happens if I measure with a tilted pole? A: If the pole is tilted, the antenna moves away from directly over the measurement point, causing horizontal displacement and also an apparent reduction in height. For example, a 5° tilt can cause a horizontal offset of several centimeters depending on the pole length. Devices without tilt compensation may see degraded accuracy even with small tilts. Therefore, as a rule, keep the pole vertical when measuring. Some high-performance GNSS receivers detect tilt with built-in sensors and apply automatic compensation, but for beginners it’s best to follow basic procedures and check verticality with a level.

Q: What if obstacles prevent placing the antenna directly over the point I want to measure? A: On site, measurement points may be next to a wall or in an area you can’t access so you can’t place the antenna directly above them. In such cases, there are several options. One is to measure at a point a fixed distance away and apply an offset correction later on drawings (for example, measure 1 m east of the design point and then apply ±1 m correction in coordinates). Another is to use the RTK app’s offset measurement function. If you specify an offset like “measure at 2 m east, 0 m north of the target point,” the app will automatically correct and compute the target point coordinates. If direct measurement is impossible, advanced methods such as measuring multiple surrounding points and using triangulation to infer the target can be employed. Choose the method appropriate to the situation.

Q: Can beginners handle RTK surveying? A: Yes. Modern RTK devices and surveying apps are designed to be user-friendly for beginners. Smartphone-based systems often let you follow on-screen instructions from antenna-height setting to starting positioning. Solutions like LRTK automatically set default offsets when you select antenna and pole types and visually indicate the positioning status (Fix or not), so even inexperienced users can operate without confusion. Of course, understanding surveying principles and precautions is important, but using current systems beginners can perform high-precision RTK surveying with confidence.

Q: What accuracy can RTK surveying provide? A: It depends on conditions, but generally RTK-GNSS can achieve horizontal accuracy of about 1–3 cm (0.4–1.2 in) and vertical accuracy of about 2–5 cm (0.8–2.0 in) under good conditions. Accuracy is more stable and can reach the 1 cm level when the base station is close and the sky is open. In environments like forests or urban canyons where satellite visibility is limited, even a fixed solution (Fix) may produce more than 5 cm (2.0 in) of error. If a Float solution remains, errors can be tens of centimeters to over 1 m (3.3 ft). To obtain stable high accuracy, capture sufficient satellites and, if possible, use multi-GNSS and dual-frequency receivers. In any case, always record data only after achieving a Fix solution to ensure high precision.