Network-based Real-time Kinematic Research Articles

Performance assessment of continuously operating reference stations using the deemed rover analysis approach with NRTK GNSS technique in Thailand

The study initiated an evaluation of the GNSS continuously operating reference stations (CORS) performance for Network-based Real-Time Kinematic (NRTK) positioning in Thailand, using the deemed rover analysis approach. Fifty CORS were selected as rovers with varying network geometries. Results indicated the highest performance, 79.9% of fixed solutions, for an average triangle side length of 54 km, while the lowest performance, 29.9%, was observed for a 93 km length with accuracies at a decimetre level. These initial explorations suggest that reducing side lengths enhances fixed solution efficiency and positioning accuracy at rovers. Occasional metre-level errors occurred, potentially linked to Internet instability.

GPS + Galileo + BDS-3 medium to long-range single-baseline RTK: an alternative for network-based RTK?

AbstractThanks to the development of the real-time kinematic (RTK) algorithm and the emerging Global Navigation Satellite System (GNSS), especially for Galileo and BeiDou-3, reliable positioning accuracy for medium and long-baseline RTK became possible globally. Moreover, with the development of the GNSS receiver hardware, baseline length limitations due to radio-based communications are removed thanks to internet-based communication. In this work, single-baseline RTK, incorporated partial ambiguity resolution with troposphere and ionosphere weighting, using GPS (G), Galileo (E), BeiDou-3 (C3) and multi-GNSS (GE and GEC3), is conducted with real GNSS data of EUREF Permanent GNSS network under three different cutoff angles (10°, 20°, and 30°) for six different lengths of baselines (~50, ~150, ~250, ~350, ~450, and ~550 km). The results show that the multi-GNSS RTK solution significantly contributed to the positioning accuracy and convergence time of the single-system RTK solutions. Based on the results, non-available epoch-wise solutions for the high-degree cutoff angles are more obvious for the single-system RTK, whereas multi-GNSS solutions provide 100% solutions for each cutoff angle and baseline. The results indicate that instantaneous and a few epochs single-epoch ambiguity resolution is feasible for 50, 150, 250 and 350 km baseline lengths for multi-GNSS RTK. Based on the positioning results, horizontal–vertical positioning improvements of multi-GNSS RTK (GEC3) compared with the single-system GPS RTK are found as 50%–37%, 40%–35%, 55%–47%, 53%–54%, 57%–49% and 57%–49% for 50, 150, 250, 350, 450 and 550 km, respectively, under a 10° cutoff angle. For 20° and 30° cutoff angles, the accuracy improvements are much higher. The convergence time improvements (n/e/u) of multi-GNSS RTK (GEC3) compared with the single-system GPS RTK are found as 86/92/75%, 77/67/72%, 75/77/83%, 53/56/52%, 69/49/62%, and 52/45/39% for 50, 150, 250, 350, 450 and 550 km, respectively, under a 10° cutoff angle.

Performance tests of geodetic receivers with tilt sensors in obstructed environments using the NRTK GNSS technique

Abstract The Department of Lands (DOL), Thailand, has adopted the Network-based Real-Time Kinematic (NRTK) Global Navigation Satellite System (GNSS) surveying technique using a Virtual Reference Station (VRS) to support cadastral surveys since 2011. Determining accurate coordinates of parcel boundary markers at building corners or near fences and walls is difficult because a GNSS range pole cannot be leveled with a circular bubble. This study aims to evaluate the performance of the receivers equipped with tilt sensors for horizontal and vertical positioning. Two types of tilt sensors used for evaluation were a magnetometer and micro-electro-mechanical system (MEMS) and an inertial measurement unit (IMU). Conducting the NRTK GNSS surveying tests was based on the pole tilt angles of 0°, 15°, 25°, 35°, and 45° from a plumb line in controlled and obstructed environments. The IMU-based tilt sensor had more advantage of accurately positioning over the MEMS sensor. The results showed that using the IMU, better than 4 cm horizontal positioning accuracy was achievable when the pole was tilted by 15° or less under non-multipath and open-sky conditions. The vertical accuracy was of a few centimeter levels and least sensitive to tilt angles using either type of sensor. However, none of the sensors precisely compensated for pole tilt in strong-multipath and complex environments, causing increased horizontal errors in decimeter levels.

The effect of GLONASS on position accuracy in CORS-TR measurements at different baseline distances

GLONASS system; It has become the second system operating on a global scale after the GPS system in the world, after completing the satellite constellation and using it at full capacity as of 8 December 2011. Due to the increasing need for high accuracy and precision real-time location information, CORS networks have become widespread in the world. In Turkey, it was established as CORS-TR and opened for use in December 2008. Comprehensive studies investigating the effects of Network-Based RTK techniques (VRS, FKP, and MAC) in the CORS-TR network are very limited due to the fact that the GLONASS system has been used at full capacity recently. In this paper, it is aimed to determine the effect of measurements derived from the Network-Based RTK techniques in the CORS-TR network of the GLONASS system on the location accuracy, and thus to make a business plan according to the accuracy and precision requirements of all civil and military users. For this purpose, simultaneous measurements were made with 6 GNSS receiver devices of the same brand and model. A total of 308,908 epoch data (northing value, easting value, and ellipsoidal height: projection coordinates (ITRF96 Datum, 2005.00 Reference Epoch)) were collected at one-second intervals in each technique and for seven days of measurements. As a result of the evaluation and analysis of the data sets obtained with the measurements; It has been observed that the GLONASS system has a positive effect on position accuracy, but in some cases, it also has disruptive effects. It has been observed that the most important contribution is to increase the number of visible satellites and to enable measurements with GLONASS satellites in cases where GPS satellites alone are not sufficient, especially in areas where the satellite elevation angle is narrowed, such as city centers, and forest areas.

Multi-GNSS-Weighted Interpolated Tropospheric Delay to Improve Long-Baseline RTK Positioning.

Until now, RTK (real-time kinematic) and NRTK (Network-based RTK) have been the most popular cm-level accurate positioning approaches based on Global Navigation Satellite System (GNSS) signals in real-time. The tropospheric delay is a major source of RTK errors, especially for medium and long baselines. This source of error is difficult to quantify due to its reliance on highly variable atmospheric humidity. In this paper, we use the NRTK approach to estimate double-differenced zenith tropospheric delays alongside ambiguities and positions based on a complete set of multi-GNSS data in a sample 6-station network in Europe. The ZTD files published by IGS were used to validate the estimated ZTDs. The results confirmed a good agreement, with an average Root Mean Squares Error (RMSE) of about 12 mm. Although multiplying the unknowns makes the mathematical model less reliable in correctly fixing integer ambiguities, adding a priori interpolated ZTD as quasi-observations can improve positioning accuracy and Integer Ambiguity Resolution (IAR) performance. In this work, weighted least-squares (WLS) were performed using the interpolation of ZTD values of near reference stations of the IGS network. When using a well-known Kriging interpolation, the weights depend on the semivariogram, and a higher network density is required to obtain the correct covariance function. Hence, we used a simple interpolation strategy, which minimized the impact of altitude variability within the network. Compared to standard RTK where ZTD is assumed to be unknown, this technique improves the positioning accuracy by about 50%. It also increased the success rate for IAR by nearly 1.

Establishment of Taiwan’s standard operating procedure for network-based RTK in cadastral surveying

Taiwan completed construction of GNSS reference stations for the network-based RTK system in 2007. The legal mode of operation used in Taiwan requires that each point be repeatedly observed for at least two observation sets separated by 60 min. This study presents a simplified field operating procedure, which measures 10 epochs of fixed solutions during each observation set and reinitializes observations 10 times. In addition, the national and local network-based RTK system were used. The average horizontal positioning accuracies were 1-3. Finally, a workflow is presented for using the network-based RTK to measure the control points in cadastral surveys.

Can Long-Range Single-Baseline RTK Provide Service in Shanghai Comparable to Network RTK?

AbstractTraditionally, GPS real-time kinematic (RTK) technique can provide precise positioning for short baselines, and network-based RTK (NRTK) is much more effective than the single-baseline RTK ...

Simulation case study of displacement monitoring using network derived positioning

Network-based real-time kinematic (NRTK) GNSS (Global Navigation Satellite System) is among the most commonly used surveying technique in many countries for various applications that requires a single GNSS receiver. The main principle of this system is to generate reliable error models that can mitigate dispersive (e.g. ionospheric delay) and non-dispersive (e.g. tropospheric delay and orbit bias) errors, which are the main sources of the degradation of positioning accuracy. In this study, the performance of NRTK positioning for deformation and landslide monitoring is investigated using a simulation apparatus. For this purpose, 20 simulated two-dimensional and vertical displacements are conducted within a two-month period in 2019. The 24-h NRTK data with 1-s sampling intervals are obtained using a CHC N72 GNSS reference receiver for each displacement. The 24-h NRTK data are mutually subdivided into 12-, 6-, 3- and 1-h non-overlapping sessions to investigate the effect of observation time on monitoring displacement performance. Two filtering methods – namely, averaging the raw observations and averaging the observations derived from Kalman filtering – are chosen for each session. The displacements obtained from the filtered NRTK observations are compared to the simulated (true) displacements. Another experiment is carried out to monitor the displacement in real time using first-order low-pass and moving-average filters. The NRTK data are collected during the displacement for a real-time experiment. The results of the experiments indicate that 1-sigma horizontal and vertical Root Mean Square errors (RMSEs) of displacements between the filtered NRTK data and true displacements are determined to be 1.5 and 5.4 mm, respectively, using 24-h data. The results also suggest that no significant difference is observed between the filtering methods for most of the points. The RMSE of the two-dimensional displacement direction between the azimuth angle derived from the filtered NRTK data and the azimuth angle of true direction is found to be 15° for 3 mm displacement using 24-h data. For detecting the displacements visually in real time, the minimum magnitude of displacements needs to be 7 mm and 10 mm for the horizontal and vertical components, respectively, to distinguish the displacements from the noise.

Performance of Network-Based RTK GNSS for the Cadastral Survey in Thailand

In Thailand, a network of GNSS Continuously Operating Reference Station (CORS) has been operating as a Network-based Real Time Kinematic (NRTK) GNSS positioning solutions since 2008. The Department of Lands designs a Thai-NRTK system mainly for GNSS cadastral survey using the Virtual Reference Station (VRS) as its positioning concept. The current Thai-NRTK consists of 114 GNSS CORSs covering only some parts of Thailand. The CORS spacing ranges from 25.1 km to198.6 km. According to previous studies, the performance of NRTK-GPS positioning determination in Thailand is strongly depending on the dimension of the triangular CORS locations; known as a “loop”. This research aims to examine the horizontal position performance of this Thai-NRTK GNSS positioning solutions as a quality indicator for GNSS cadastral surveying. The test was carried out with quite a large number of test samples (total of 2,122 points) and where every loop is separated into 4 test groups with differing the station distances starting from the loop spacing of: 30 km to 50 km, 50 km to 70 km, 70 km to 90 km and 90 km to 110 km, respectively. The positioning performance test is conducted in two main folds; namely, positioning accuracy and time to resolve its solutions. On positioning accuracy, the test results show that the spacing of every tested loop achieves the accuracy in accordance with the cadastral surveying requirements. This proves that the Thai-NRTK GNSS positioning network and technique is well-designed and suitable for cadastral positioning within its coverage areas. On time to resolve fixed solution, the test results indicate that the ‘time to first fixed’ and the ‘rate of the horizontal position jump’ increase with longer loop distance; whereby only loop length of 30 km to 50 km has 100% success ‘rate of ambiguity-fixing’ solutions; therefore, in order to achieve a high reliable performance positioning from the Thai-NRTK GNSS solutions for cadastral survey in Thailand, it is recommended that the reference stations shall be kept within 50 km.

High Precision GNSS Positioning for the Coastal Navigation Safety of Large Vessels

Bae, T.-S. and Kim, M., 2019. High precision GNSS positioning for the coastal navigation safety of large vessels. In: Lee, J.L.; Yoon, J.-S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 441-445. Coconut Creek (Florida), ISSN 0749-0208.Over several decades, the Global Navigation Satellite System (GNSS) has been the most important navigation equipment for vessels. Although the C/A code based absolute positioning is sufficient for most cases, a precisely guided coastal navigation is necessary for the entry and the departure of large vessels at a port. More accurate positioning and navigation can be achieved by applying the real-time kinematic (RTK) technique, which uses the carrier phases of the GNSS signals. However, the error is generally proportional to the baseline lengths between the references and the rovers due to the decorrelation of the signals. In this study, the error behavior of a single-baseline RTK (SRTK) was analyzed based on a Continuously Operating Reference Station (CORS) network in Korea. In addition, the network-based RTK (NRTK) correction was used to better estimate the position of large vessels for coastal navigation. Finally, the UP component of the vessel was constrained to the geoid to characterize coastal navigation uniquely.

Network-based RTK Performance for Drone Navigation

The Real-time Kinematic (RTK) was predominantly used for the positioning of the ground applications including moving vehicles. Due to the limited baseline lengths, the Network-based RTK (NRTK) was introduced since late-1990s, and successfully applied to the high precision surveying purposes for more than a decade. We conducted the experiments to analyze the performance of the single-baseline RTK (SRTK) as well as the NRTK using one of the operational NRTK systems of Korea, which is the Virtual Reference Stations (VRS) technique. A total of 46 Continuously Operating Reference Stations (CORS) are used for both SRTK and NRTK to secure the redundancy of the baseline lengths. Since the CORS are quite evenly located at an average of 50-60 km, the analysis of error behavior is restricted in terms of seamless variation of baseline length. Therefore, on top of the existing CORS, we simulated the GNSS RINEX data of the rover (that is, the drone position) at a specific location to get the uniform distribution to the reference stations. Furthermore, the rover was generated for different altitude to evaluate the performance of vertical component of the NRTK system. The CORS GNSS data were obtained at 1 Hz in RINEX format, and the low-cost receiver (ublox) was used for the rover with same interval, single-frequency capability. The correction information from the NRTK server was simultaneously logged for post-processing using the open source software RTKLIB. The percentage of ambiguity resolution was quite reasonable up to 50 km, and drastically drops down as the baseline gets longer. The generated VRS was located with an offset of a few meters in a certain direction, and the horizontal errors also showed a similar pattern. The vertical error behavior due to the tropospheric model deficiency should also be analyzed further.

PPP-RTK based on undifferenced and uncombined observations: theoretical and practical aspects

A synthesis of two prevailing global navigation satellite system positioning technologies, namely the precise point positioning and the network-based real-time kinematic, results in the emergence of the PPP-RTK, enabling single-receiver users to achieve high positioning accuracy with reasonable timeliness through integer ambiguity resolution. The realization of PPP-RTK needs to accomplish two sequential tasks. The first task is to determine a class of corrections including, among others, the satellite phase biases (SPBs) at the network level. With these corrections, the second task, then, is to solve for the ambiguity-fixed, absolute position at the user level. In this contribution, we revisit three variants (geometry-free, geometry-fixed and geometry-plus-satellite-clock-fixed) of the undifferenced and uncombined PPP-RTK network model and then point out their implications for practical use. We also carry out a case study using multi-day, dual-frequency global positioning system data from the crustal movement observation network of China stations, aiming to figure out what are the most appropriate linear combinations of the SPBs to be transmitted to the users from the viewpoint of decorrelation, and to assess the static and kinematic positioning performance.

Temporal correlation length of network based rtk techniques

Temporal correlation in network based Real-Time Kinematic (NRTK) data exists due to the unmodeled multipath, tropospheric (especially for wet delay) and ionospheric variations, and slowly changing spatial geometry of satellites. Ignoring the temporal correlation can result in too much confidence being placed in the estimated uncertainty of the coordinates. Temporally correlated errors occur when the magnitude of an error is constant or similar over time. In this study, temporal correlation lengths of commonly used Virtual Reference Station (VRS), Flächen Korrektur Parameter (FKP) and Master Auxiliary Concept (MAC) NRTK techniques were computed for the different length of baselines between the rover and the master station (closest CORS station) in the Turkish GNSS active network (TUSAGA-Aktif). Thus, appropriate time separation between the measurements for revisits of the points was determined in order to avoid overly optimistic coordinate uncertainty and unreliable coordinate checking. The results show that there is no clear relationship between the correlation length and the baseline distance. Correlation lengths of FKP and VRS are similar, whereas MAC produced a much longer correlation time for the horizontal component. When the correlation length of each technique is averaged, the correlation lengths are estimated as 17–13–16 min for northing, easting projection coordinates and ellipsoidal height, respectively. According to the measurements using different geodetic-grade receivers, the results show that temporal correlation length varies between the receivers.

A New Algorithm for High-Integrity Detection and Compensation of Dual-Frequency Cycle Slip under Severe Ionospheric Storm Conditions.

Many strategies for treating dual-frequency cycle slip, which can seriously affect the performance of a carrier-phase-based positioning system, have been studied over the years. However, the legacy method using the Melbourne-Wübbena (MW) combination and ionosphere combination is vulnerable to pseudorange multipath effects and high ionospheric storms. In this paper, we propose a robust algorithm to detect and repair dual-frequency cycle slip for the network-based real-time kinematic (RTK) system which generates high-precision corrections for users. Two independent and complementary carrier-phase combinations, called the ionospheric negative and positive combinations in this paper, are employed for avoiding insensitive pairs. In addition, they are treated as second-order time differences to reduce the impact of ionospheric delay even under severe ionospheric storm. We verified that the actual error distributions of these monitoring values can be sufficiently bounded by the normal Gaussian distribution. Consequently, we demonstrated that the proposed method ensures high-integrity performance with a maximum probability of missed detection of 7.5 × 10−9 under a desired false-alarm probability of 10−5. Furthermore, we introduce a LAMBDA-based cycle slip compensation method, which has a failure rate of 1.4 × 10−8. Through an algorithm verification test using data collected under a severe ionospheric storm, we confirmed that artificially inserted cycle slips are successfully detected and compensated for. Thus, the proposed method is confirmed to be effective for handling dual-frequency cycle slips of the network RTK system.

Assessing the accuracy of NRTK altimetric positioning for precision agriculture: test results in an olive grove environment in Southeast Spain

Soil erosion modeling in olive groves requires precise and accurate spatial data for the representation of topography associated with each time epoch considered. The precision and accuracy of altimetric values affect the quality of the digital elevation model (DEM) and therefore these requirements must be added to the necessity to generate high resolution DEMs. The increase of quality implies: 1. Improving the quality of the instrumentation and methodology applied in the field data collection and 2. Minimizing errors from the interpolation algorithm used to generate the digital terrain model. Currently, RTK networks are an indispensable complement to global navigation satellite systems (GNSS) precise positioning. The availability of highly accurate three-dimensional real time positioning has opened the door to new applications, making network-based real time kinematic (NRTK) positioning an attractive spatial data source for modeling soil erosion in small areas. This paper analyzes the quality of NRTK altimetric positioning supported by a local active network and its application in a test olive grove in SE Spain for soil erosion modeling. An evaluation procedure was implemented at several test sites distributed throughout an olive grove environment with special emphasis on filtering and checking the NRTK solutions in the vertical component. The precision in this component revealed a mean value of 15 mm and the vertical accuracy reached maximum values of 30 mm. In order to generate high resolution and accuracy DEM from the NRTK data, cross sections on the test olive grove were surveyed. The average altimetric quality value (CQ1D) of points surveyed was 0.017 m, according to the standard deviation estimated at test points. Based on the quality results, NRTK positioning is an accurate and reliable methodology for monitoring the erosion processes of small areas in an olive grove environment.

Accuracy and precision of network-based RTK techniques as a function of baseline distance and occupation time

Turkey established the TUSAGA-AKTIF CORS Network in May 2009. Network software and central server were updated in 2016. With this update, GLONASS message type was determined for Flachen Korrektur Parameter (FKP), Master Auxiliary Concept (MAC) and Virtual Reference Station (VRS) network-based real time kinematic (NRTK) techniques. A 64 bit central server and the Trimble Pivot Platform network software were also acquired with this update. To the best of our knowledge, there has not been a comprehensive accuracy and precision test of the new system yet. In this paper, we aimed to create empirical accuracy and precision model of FKP, MAC and VRS NRTK techniques of the updated system as a function of baseline distance and occupation time. It is intended that surveyors can perform mission planning according to the requirements of accuracy and precision using these models. Seven test points and two check points were chosen to conduct the experiment. The baseline lengths with respect to the closest continuously operating reference stations (CORS) station were determined as 5-20-40-50 km approximately. Three thousand epochs with 2-s sampling interval were obtained for northing, easting and ellipsoidal height coordinate components of NRTK techniques at each point. Assumed true coordinates of each test point were determined by static survey using the GAMIT/GLOBK scientific software. In terms of accuracy and precision, our results show that empirical accuracy model depends only on the occupation time while empirical precision model depends on both the baseline length with respect to the closest CORS station and the occupation time for each NRTK technique. The results indicate that estimated accuracy and precision models can be safely used for mission planning purposes.

Performance Analysis of Network-RTK Techniques for Drone Navigation considering Ionospheric Conditions

Recently, an accurate positioning has become the kernel of autonomous navigation with the rapid growth of drones including mapping purpose. The Network-based Real-time Kinematic (NRTK) system was predominantly used for precision positioning in many fields such as surveying and agriculture, mostly in static mode or low-speed operation. The NRTK positioning, in general, shows much better performance with the fixed integer ambiguities. However, the success rate of the ambiguity resolution is highly dependent on the ionospheric condition and the surrounding environment of Global Navigation Satellite System (GNSS) positioning, which particularly corresponds to the low-cost GNSS receivers. We analyzed the effects of the ionospheric conditions on the GNSS NRTK, as well as the possibility of applying the mobile NRTK to drone navigation for mapping. Two NRTK systems in operation were analyzed during a period of high ionospheric conditions, and the accuracy and the performance were compared for several operational cases. The test results show that a submeter accuracy is available even with float ambiguity under a favorable condition (i.e., visibility of the satellites as well as stable ionosphere). We still need to consider how to deal with ionospheric disturbances which may prevent NRTK positioning.

Instantaneous BDS + GPS undifferenced NRTK positioning with dynamic atmospheric constraints

As the Chinese BeiDou Navigation Satellite System (BDS) has become operational in the Asia-Pacific region, it is important to better understand and demonstrate the benefits of combining triple-frequency BDS with dual-frequency GPS observations for network-based real-time kinematic (NRTK) services. Undifferenced NRTK is a new NRTK service mode, it extends the concept of NRTK by not requiring reference station and specified reference satellite at the rover processing. In order to realize the undifferenced NRTK service, a strategy for real-time modeling the undifferenced (UD) augmentation information is given, in which the fixed double-differenced ambiguities are transformed into UD ones with the help of datum settings. Since this strategy is insensitive to existing ephemeris products, it is applicable to the services of current BDS regional reference networks. Furthermore, a processing scheme for ambiguity resolution (AR) with arbitrary-frequency observations is also presented in detail. An instantaneous and reliable BDS + GPS positioning service can be provided to the rovers in undifferenced NRTK processing mode. With the data collected at 31 stations from a continuously operating reference station network in Guangdong Province (GDCORS) of China, the efficiency of the proposed approaches using combined BDS and GPS observations is confirmed. For three rover stations during days 327–329, a total of 12,960 1-min tests were performed separately to demonstrate the performance of AR. Thanks to the dynamically refined priori information of residual tropospheric and ionospheric error, and the availability of more satellites and observations, the AR fixing rates of combined BDS and GPS systems improve by 13 to 65%, compared with those of the GPS-only system using the traditional WL-L1-IF scheme. The positioning accuracy has also significantly improved.

High ionospheric activity effects on LatPos RTK network performance in Latvia

Fast and reliable coordinate determination with GNSS in real time is the main objective of continuous operating reference system (CORS) network users. To provide services for coordinate determination, Network-based Real Time Kinematic (NRTK) system called “LatPos” has been established and operated in Latvia since 2006. One of the factors, affecting the performance of LatPos system services, is activity of ionosphere. Ionosphere is a region of the earth’s atmosphere, from about 60 kilometers up to 1000 km above the earth’s surface, in which there is a high concentration of free electrons, spatially variated, affected by space weather, seasonal and solar cycle changes.Ionospheric activity conditions depending on mentioned factors can be analyzed by LatPos system data. Some data processing strategies has been developed and LatPos RTK network performance results obtained, during different ionospheric activity conditions. This paper focused on both segments: the NRTK performance and the rover receiver coordinate determination possibilities in field when high ionospheric activity occurs.

Investigation of network-based RTK techniques: a case study in urban area

Network-based real-time kinematic (NRTK) GNSS (Global Navigation Satellite System) positioning system is one of the most commonly used in many countries for various applications which require instant and highly accurate positioning all around the clock. The main principle of this system is to generate reliable error models that can mitigate dispersive (e.g., ionospheric delay) and non-dispersive (e.g., tropospheric delay and orbit biases) errors which are the main sources for the degradation of the positioning accuracy. There are several correction techniques that have been implemented and used in NRTK concept. The objective of this study is to evaluate accuracy, precision, time to first fix (TTFF), and performance of carrier phase ambiguity fixing while maintaining the same survey conditions for VRS, FKP, and MAC NRTK techniques. The Turkish TUSAGA-Aktif CORS network was used to obtain the three NRTK corrections. In terms of accuracy, our results show that all the techniques are practically the same and the horizontal positioning accuracy is in the order of few centimeters for all techniques. As far as precision and TTFF are concerned, VRS produced slightly better results comparing to the others. When it comes to ambiguity fixing performance in the dynamic environment, FKP produced the best results.