CORS Station Research Articles

Assessment of Ground Control Points Positional Shift and Management Practices: Evidences from Assosa Town, Western Ethiopia

This study assesses the positional shift of existing control points and management practices found in and around Assosa town. The static GPS measurement technique was used as an independent source and a point wise method were used to assess the positional shift and accuracy level evaluation. Due to unavailability of local CORS station, two first order GCPs were used as a reference during static GPS measurement. After measurement was conducted depending on the baseline length between control point marks, the STC desktop software and online CSRS-PPP post processing technique was used. Thus, the positional accuracy of selected GCPs of STC Post processing technique has a mean error of 0.324 m and whereas the GCPs of CSRS-PPP has a mean error of 0.571 m. Horizontal distance error obtained with the STC differential technique is ranging from 0 to 0.83 m which is inconsistent relative to the range 0.437 m to 0.815 m obtained from online CSRS-PPP solution. The positional accuracy of GCPs was also assessed using horizontal distance error of both processed techniques. The positional accuracy of GCPs at 95% confidence level is between -0.117 m and 0.765 m with STC and between 0.395 m and 0.747 m in online CSRS-PPP solution. Based on the result, the accuracy level of existing GCPs found in Assosa town, does not meet the FGDC accuracy. This was mainly associated with perception of communities on ground control point management activities. The study revealed almost low communities practice and control point management responsiveness. Finally, study suggested that there should be participatory guidance to establish and manage the ground control points.

CORS station for synergistic monitoring of multivariate surface parameters in expansive soils

Expansive soils cause frequent surface deformation due to their expansion and contraction, which is a serious engineering hazard, and long-term subsidence monitoring is a prerequisite for preventing and controlling expansive soil disasters. Currently, the conventional monitoring methods for the above issue include Interferometric Synthetic Aperture Radar (InSAR) technology, but InSAR is not suitable for uninterrupted monitoring of surface deformation and has low sensitivity. Meanwhile, it can’t obtain multiple surface environmental parameters around the station. The Global Navigation Satellite System (GNSS), a system that can directly acquire surface deformation, has been widely used in landslide disaster monitoring, and in recent years, this technology has also been applied to the field of expansive soil disaster monitoring. At the same time, GNSS can also provide a constant stream of L-band microwave signals to obtain ground environmental information such as precipitable rainfall and soil moisture around the station. In previous studies of expansive soil hazards, GNSS technology has been mainly used to provide surface deformation information without exploring its potential to invert ground environmental information around stations. This paper proposes a ground-based GNSS remote sensing integrated monitoring system that integrates expanding land surface parameters such as “precipitable rainfall, soil moisture, and three-dimensional deformation” and analyses the ability of ground-based GNSS to be used for integrated monitoring of expanding soil hazards by combining ten years of consecutive observational data from GNSS stations along the coastal area of Houston. The experimental results show that the GNSS is capable of providing highly accurate time-series characterization of deformation, and inelastic subsidence in recent years has resulted in a cumulative permanent elevation loss of 2 cm along the Houston coast. The correlation coefficient between soil moisture extracted by the fifth-generation European reanalysis data (ERA5) and soil moisture inverted by ground-based GNSS is 0.514. At the same time, the GNSS was also able to monitor the zenithal precipitable water vapor (PWV) and soil moisture changes around the GNSS station and further analyze the response relationship among the three parameters, which could comprehensively evaluate the stability of expansive soils, avoiding the unreliability of relying on a single piece of monitoring information to assess the stability of expansive soils. We hope to construct a more comprehensive ground-based GNSS remote sensing monitoring system to better monitor expansive soil hazards.

Monitoring subsidence of open pit mine slope based on GNSS/CORS technology - case study at the Coc Sau open-pit coal mine

Subsidence value is one of the important parameters to evaluate the stability of open pit mine slope. The subsidence is determined from height values measured at different times using different methods and equipment. When applying GNSS/CORS technology to monitor displacement, landslides, ground subsidence or structures, a specialized monitoring system is needed to ensure the necessary accuracy. This article presents the results of research on subsidence monitoring of open pit mine slope based on CORS technology and a self-developed GNSS receiver. The CORS station is set up with Trimble's Zyphir 2 Geodetic antenna and Stonex GNSS receiver located in Cam Pha city, Quang Ninh. The GNSS receiver for monitoring station is designed and developed based on the Trimble's GNSS BD970 board and integrated with a 4G wifi modem, allowing the transmission of monitoring data in standard NMEA0183 format to the CORS station's host computer. Decoded monitoring data and error filtering have improved the accuracy of height determination achieved at the mm level. Results of simulation experiments and experiments with actual monitoring data at Coc Sau coal mine, Cam Pha, Quang Ninh have proven the effectiveness and reliability of the method. With simulated experimental monitoring results, it shows that the largest subsidence difference is 16 mm and the smallest is 6 mm.

Spatial-Temporal Dynamic Evolution of Land Deformation Driven by Hydrological Signals around Chaohu Lake.

The frequent occurrence of extreme climate events has a significant impact on people's lives. Heavy rainfall can lead to an increase of regional Terrestrial Water Storage (TWS), which will cause land subsidence due to the influence of hydrological load. At present, regional TWS is mostly obtained from Gravity Recovery and Climate Experiment (GRACE) data, but the method has limitations for small areas. This paper used water level and flow data as hydrological signals to study the land subsidence caused by heavy rainfall in the Chaohu Lake area of East China (June 2016-August 2016). Pearson's correlation coefficient was used to study the interconnection between water resource changes and Global Navigation Satellites System (GNSS) vertical displacement. Meanwhile, to address the reliability of the research results, combined with the Coefficient of determination method, the research findings were validated by using different institutional models. The results showed that: (1) During heavy rainfall, the vertical displacement caused by atmospheric load was larger than non-tidal oceanic load, and the influence trends of the two were opposite. (2) The rapidly increasing hydrologic load in the Chaohu Lake area resulted in greater subsidence displacement at the closer CORS station (CHCH station) than the more distant CORS station (LALA station). The Pearson correlation coefficients between the vertical displacement and water level were as high as -0.80 and -0.64, respectively. The phenomenon confirmed the elastic deformation principle of disc load. (3) Although there was a systematic bias between the different environmental load deformation models, the deformation trends were generally consistent with the GNSS monitoring results. The average Coefficients of determination between the different models and the GNSS results were 0.63 and 0.77, respectively. The results demonstrated the effectiveness of GNSS in monitoring short-term hydrological load. This study reveals the spatial-temporal evolution of land deformation during heavy rainfall around Chaohu Lake, which is of reference significance for water resource management and infrastructure maintenance in this area.

Long term subsidence rate in Pekalongan city observed by SAR Interferometry

Land subsidence occur in some large cities in Java Island, Indonesia. Among those cities, Pekalongan suffer relatively large and consistent rate of land subsidence compared to other cities. Impact of this long-term land subsidence manifested as worsen of flood, infrastructure damage, and decline of ground water quality. To see the continuation of land subsidence in Pekalongan, we use Sentinel-1 data from 2016 to 2023 from both ascending and descending direction to spatio-temporaly mapped both magnitude and rate of the land subsidence. Persistent Scatterer InSAR (PS-InSAR) method is used to process the SAR data, also use DEMNAS and Generic Atmospheric Correction Online Service (GACOS) to reduce topographic and atmospheric error consecutively. We use CPKL CORS station, which managed by Badan Informasi Geospasial (BIG) for control point for the final subsidence rate calculation. Our result show that the area of subsidence does not change significantly for the last 7 years, with the maximum rate reach 16 cm/year of subsidence occur in the western side of Pekalongan City. However, the land subsidence also occurs in the coastal part with lower rate of 5 cm/year. The subsidence rate in most of the places are constant, with exception during 2020-2021 period.

Case study on a novel approach to determining initial values for 3D water vapor tomography in the a priori water vapor field

Insufficient prior information in GNSS water vapor tomographic models can lead to instability in the structure of the design matrix. The addition of high-precision initial values for water vapor density can effectively solve this problem, but common methods for obtaining water vapor density are relatively crude and not fully utilizing the original accuracy of the a priori water vapor field. To address this issue, a new method is proposed that takes into account the influence of the a priori information weight ratio in the tomographic model on tomographic analysis results, based on the negative exponential decrease of atmospheric water vapor density in the vertical direction with height. Moreover, the 3D water vapor tomographic technique based on the ray-tracing fast voxel traversal algorithm has been improved and implemented in the C++ programming language. To verify the feasibility, accuracy, and stability of the improved 3D water vapor tomographic technique and the proposed method, the experiment using actual data from the CORS station in Hong Kong in January and May and the corresponding grid data provided by ERA5 was conducted. As benchmarks, radio-sounding data from the experimental area was utilized. In May, the proposed method exhibited an average daily improvement in the root mean square error of 0.88% (UTC0) and 0.97% (UTC12), and an improvement in the interquartile range of the difference between the water vapor density values at each altitude layer (excluding the top and bottom layers) and the corresponding sounding data of 5.08% (UTC0) and 3.37% (UTC12). In January, the average daily improvement in the root mean square error was −13.78% (UTC0) and −4.84% (UTC12), and the improvement in the interquartile range of the difference between the water vapor density values at each altitude level and those calculated from the corresponding sounding data was −14.49% (UTC0) and −6.31% (UTC12). The results show that the proposed method and the commonly used method maintain high consistency in the accuracy of the water vapor density values solved by the system of tomographic equations and improve stability, especially in May when the water vapor density near the surface is high. The feasibility of the improved 3D water vapor tomographic technique based on the ray-tracing fast voxel traversal algorithm is also demonstrated.

Research and Evaluation on Dynamic Maintenance of an Elevation Datum Based on CORS Network Deformation

This paper presents a method for dynamically maintaining a regional elevation datum using CORS stations as core nodes. By utilizing CORS station data and surface mass loading data (including land water storage, sea level, and atmospheric pressure), the normal height changes of each station can be determined and dynamically maintained. The validity of this method is verified using multiple leveling survey results from five CORS stations in Beijing’s subsidence area between January 2012 and June 2021. Results show that it is necessary to derive and correct the height anomaly variation of CORS stations caused by surface mass loading using the remove-calculate-restore method and the Green’s function integration method, with the influence of surface mass changes reaching a subcentimeter level. CORS stations exhibiting great observation quality achieve a mean accuracy of 2.7 mm in determining normal height changes. Such accuracy surpasses the requirements of second-class leveling surveys covering route lengths exceeding 1.35 km, as well as conforming/closed loop routes with distances greater than 0.46 km. By strategically selecting CORS stations with long-term continuous observations and high-quality data as core nodes within the elevation control network, dynamic maintenance of the regional elevation datum can be achieved based on CORS station data.

Performance evaluation of single and double-frequency low-cost GNSS receivers in static relative mode

The advancement of low-cost GNSS receivers with modern built-up characteristics has opened a new window to investigate the performance of various low-cost receivers with an outlook on their performance and suitability for varied geodetic purposes. The main objective of this study is to evaluate the positioning performance of single and double-frequency GNSS receivers in combination with geodetic antennas in static relative mode regarding Mexican regulations. The recorded observations were processed by a static relative method including the CORS station from the National Institute of Statistics and Geography in Mexico (INEGI). The results of the survey conducted at a distance of 4 and 33 km from CORS station show similar accuracy for all low-cost receivers. For low-cost GNSS receivers NEO-M8T, NEO-6T, and ZED-F9P the solutions that were obtained reached mm in horizontal precision using a geodetic grade antenna. Similarly, the ZED-F9P model was proved at a long distance from the CORS station and presents high precision. Regarding the vertical component, in all cases where the GGM10 model was included, the vertical component is not allowed to use for topography or geodetic works, however, the horizontal component where mm precision was achieved is allowed for different highly precision survey works.

A Height Nonlinear Velocity Field Algorithm for CORS Station Based on GARCH Model.

In this study, the basic concept of height nonlinear velocity field modeling in the CORS station is described. The noise results in a large deviation between the observation and predicted height. An ARCH testing method for heteroscedasticity of CORS height residual square series was proposed and the non-stationary characteristic of CORS height residual square time series was proved. A CORS height nonlinear velocity field reconstruction method based on the GARCH model was proposed. First, a nonlinear LS periodic fitting model was established for CORS height series data. Then, a GARCH model was established for the fitted non-stationary residual series. Finally, the signal term, linear trend term, and GARCH model noise term of nonlinear LS modeling were combined to reconstruct the nonlinear velocity field of the CORS height. The RMSE of nonlinear LS cycle modeling for 25 CORS stations worldwide ranged from 5 to 10 mm. The differences between the velocity, approximate annual and semi-annual amplitudes, and SOPAC results were 0.73 mm/a, 0.94 mm, and 0.51 mm, respectively. Compared with the centimeter amplitude of the CORS station height, the accuracy of the nonlinear model established in this study met the requirements. The results of height nonlinear velocity field reconstruction at 25 CORS stations worldwide showed that the mean square error of prediction of the one-year height movement reached 9 mm, and the average prediction accuracy of the semi-annual was 7 mm. Compared with the calculation accuracy of the current global CORS elevation component of 3–5 mm, the prediction error in this study was about 3 mm. The expected goal was achieved regarding the accuracy of the CORS station height nonlinear velocity field model.

Investigation in designing and developing the GNSS positioning instrumentation used in measurement and mapping by CORS/RTK technology

Currently, in addition to GNSS receivers manufactured by foreign companies and imported into Vietnam, there are some domestically produced products with lower prices on the market. This paper presents an investigation on the design and development of a low-cost and high-precision GNSS device, used for CORS/RTK measurement in establishing topographic and cadastral maps. The developed GNSS device consists of a GNSS satellite antenna, a receiver, and an electronic field-book (using a smartphone device) installed with a self - developed software. The GNSS receiver is developed based on the technology and equipment of Drotek company (France). The components of the GNSS receiver have been selected and designed with functionality for both dynamic and static measurement modes. The GNSS receiver and electronic field-book are connected wirelessly via the Bluetooth module, allowing convenient operation with the receiver. Experiments were conducted to measure the parallel points of an established geodetic network using GPS technology. The possitioning data was measured by two receivers, South’s S82 (China) and self-developed KX20-R, using RTK method with a single CORS station installed at the University of Mining and Geology. The results showed that the developed GNSS positioning device provides an accuracy of centimeters and completely meet the requirements of large-scale topographic and cadastral surveying and mapping.

Ionosphere Anomaly Analysis before Earthquake Using GPS (Case Study: Banten Earthquake August 2nd, 2019)

This research is to analyze anomalies in the ionosphere that occur when an earthquake occurs. When an earthquake occurs, three types of waves are generated, namely: acoustic waves, gravity waves, and reyleigh waves. Acoustic waves generated perpendicularly from the earth’s crust during an earthquake propagate into the ionosphere, where they create electron density deviations. This phenomenon is detected as CIDs (Coseismic Ionosphere Disturbances), namely TEC (Total Electron Content) fluctuations that occur 15 minutes to 1 hour after an earthquake occurs. As a result of this deviation, the electromagnetic waves emitted by the GNSS (Global Navigation Satellite System) satellite will delay when passing through an ionosphere of approximately 300 km from the earth’s surface. The earthquake data used in this study came from earthquakes in Indonesia with the potential for a tsunami, namely the Banten earthquake on August 2, 2019 (7.4Mw from BMKG) with GNSS data from the closest CORS station to the epicenter, namely the CPTN, CPTU, and CUJG stations. The processing results show that there is a TEC anomaly recorded by GPS satellite no. 29 which appears 15-20 minutes after the earthquake. Anomalies ionosphere that occurs during an earthquake are expected to be useful as an early warning system before a tsunami happened.

Coseismic Ground Displacement after the Mw6.2 Earthquake in NW Croatia Determined from Sentinel-1 and GNSS CORS Data

At the very end of the year 2020, on 29 December, a hazardous earthquake of Mw = 6.2 hit the area of Petrinja and its surroundings, in the NW of Croatia. The earthquake was felt across the area of 400 km, leaving an inconceivable damage in the vicinity of the epicenter, devastated towns and ruined lives. In order to map the spreading of earthquake waves and to determine the coseismic ground displacement after the mainshock, we have analyzed open satellite radar images of Sentinel-1 and the GNSS data from the nearest CORS station related to the epicenter, along with the seismic faults. In this paper, we addressed and mapped the displacement linear surface ruptures detected by the SAR interferometry. The results show the vertical ground displacement to the extent of −12 cm in the southern area and up to 22 cm in the north-western part of a wide area struck by the earthquake impact, related to the epicenter. Subsidence and uplift in a range of ±5 cm over a wider affected area indicate a spatial extent and hazardous impact made by the earthquake. The ground displacement of 30 cm to the West and 40 cm to the East has been identified considering the intersection of Pokupsko and Petrinja strike-slip fault system in the seismic zone of Pannonian basin. Accordingly, we obtained matching results of 5 cm south-easting shift and −3 cm subsidence on Sisak GNSS CROPOS station, addressing the tectonic blocks movement along the activated complex fault system. The results compared with the geology data confirm the existence of two main faults; the Pokupsko and the Petrinja strike-slip faults and interpret the occurrence of secondary post-seismic events over the observed area.

GNSS/CORS-Based Technology for Real-Time Monitoring of Landslides on Waste Dump – A Case Study at the Deo Nai South Dump, Vietnam

Nowadays, there are many different methods for monitoring waste dump landslides based on GPS, total station, remote sensing, UAV, Lidar, etc. However, these technologies can only periodically monitor but cannot continuously monitor in real time. In recent years, GNSS CORS technology has been applied to continuously monitor real time waste dump landslides in open-pit mines to provide immediate or nearly-instant warning of waste dump landslides, which can timely prevent and minimize damages to property and human life. In the present work, the real time monitoring system of waste dump landslides monitoring based on GNSS CORS technology was designed and built. This real time monitoring system includes (1) the GNSS CORS station based on Leica technology, (2) the monitoring stations system, (3) the data collection, transmission and processing system based on Trimble technology and the warning system. This system allows continuous monitoring in real time and provides an instant warning if the landslide occurred. Moreover, it also has the advantage of being cheap, flexible and easy to install for monitoring stations. A simulation experiment results showed that our monitoring system operates stably and continuously 24/7 with a horizontal accuracy of ±3 mm and vertical accuracy of ±5 mm.

Experimental Work for Evaluation the Time Saving Between Different GPS Techniques for Makkah- Jeddah Region

Nowadays, there are available in technology, devices, Techniques such as GNSS and CORS and use the VRS techniques. Although for previous technology, some application just needs for the ordinary GPS techniques. So, the current research work is done by field experiments to assess the time saving and accuracy between GPS different techniques such as Stop & Go, Kinematic, and Kinematic ON THE FLY Techniques especially in mountain areas like MAKKAH region. There are three post-processed GPS kinematic techniques. These techniques are stop &go, kinematic, and kinematic on the fly techniques. Stop& go and kinematic techniques require the so-called initialization process, which must be repeated in each cycle slip due to satellite-signal blockage. This is a time consuming and practically reduces the surveying productivity. On the other hand, the kinematic on the fly technique does not require the initialization process. This leads to increase the surveying productivity. The current paper makes a comparative study between GPS stop &go, kinematic, and kinematic on the fly techniques, from points of view of accuracy, time elapsed for the initialization process, observation time for each surveyed point and the surveying productivity. The results supported by appropriate statistical tests showed that positional discrepancies between stop-go and kinematic techniques have mean value of 22 mm  (S.D) of ± 7 mm. Also, the positional discrepancies between the stop& go and kinematic on the techniques are statically and practically insignificant, where the results showed that the positional discrepancy between the two techniques has a mean value of 22 mm with  (S.D) of ± 2 mm. In this context, the kinematic on the fly technique is increasing the surveying due to using a recording data of about 3-seconds for each surveying point, and also because this technique does not require any initialization process which takes a lot of time especially in case of surveying near tree, road, mountains, and advertising frames specially when internet and communication with the CORS station is missed or disconnected. Finally, in case the issues to use RTK or VRS due to communication problems specially the regions within mountains areas such as MAKKAH in this situation the GPS kinematic on the fly technique is highly recommended to replace the stop-go and kinematic techniques, in all the surveying works of medium scale. Also, the distance between the surveyed point and the reference receiver does not affect the resulted coordinates for about 7 km.

Investigation and design of monitoring systems in real time landslides at Xekaman 3 hydropower plant

This paper presents results of investigating, designing, and building a monitoring system in real-time based on GNSS CORS technology in order to monitor landslides at Xekaman 3 hydropower plant in the Lao people’s Democratic Republic. A system with 18 monitoring stations and a CORS station has been designed to ensure the operation of system 24/7. The connection diagram for data transmission from the monitoring stations to the data processing center, as well as the connection diagram of the devices at a monitoring station has been designed. A simulation experiment has shown that the designed system can be applied for real-time monitoring of landslide.

DATA QUALITY CHECK AND VISUAL ANALYSIS OF CORS STATION BASED ON ANUBIS SOFTWARE

Abstract. Aiming at the observation data of CORS multi-mode data quality and inspection in CORS station, based on the observation data of a CORS station in Guilin, Guangxi, the paper used TEQC and Anubis software to check the data quality from data utilization, cycle slip ratio and multipath. The results show that the three quality inspection indicators of Anubis software are better than TEQC software, which proves that Anubis' data quality inspection results are effective and reliable. On this basis, using Anubis drawing tools to perform quality inspection and visual analysis from satellite constellation, signal band and observation data itself, it shows that Anubis' visual content is more elaborate than TEQC, and users can more intuitively understand and control the data quality of CORS station.

GEOMETRIC ASPECTS EVALUATION OF GNSS CONTROL NETWORK FOR DEFORMATION MONITORING IN THE JATIGEDE DAM REGION

Many factors led to dam construction failure so that deformation monitoring activities is needed in the area of the dam. Deformation monitoring is performed in order to detect a displacement at the control points of the dam. Jatigede Dam deformation monitoring system has been installed and started to operate, but there has been no evaluation of the geometry quality of control networks treated with IGS points for GNSS networks processing. Therefore, this study aims to evaluate the geometric quality of GNSS control networks on deformation monitoring of Jatigede Dam area. This research data includes the GNSS measurements of five CORS Jatigede Dam stations (R01, GG01, GCP04, GCP06, and GCP08) at doy 233 with network configuration scenarios of 12 IGS points on two quadrants (jat1), three quadrants (jat2), and four quadrants (jat3 and jat4). GNSS networks processing was done by GAMIT to obtain baseline vectors, followed by network processing usingparameter method of least squares adjustment. Networks processing with least squares adjustment aims to determine the most optimal by precision and reliability criterion. Results of this study indicate that network configuration with 12 IGS stations in the two quadrants provides the most accurate coordinates of CORS dam stations. Standard deviations value of CORS station given by jat1 configuration are in the range of 2.7 up to 4.1 cm in X-Z components, whereas standard deviations in the Y component are in the range 5.8 up to 6.9 cm. An optimization assessment based on network strength, precision, and reliability factors shows optimum configuration by jat1.

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.

Technical challenges of airborne LiDAR surveying technology in Malaysia

Light Detection and Ranging (LiDAR) is one of the most recent and useful active remote sensing tools; it provides accurate horizontal and vertical information by direct time measurement of a short laser pulse’s reflection on the Earth surface. The ability of LiDAR data to accurately characterize terrain has led many users in Malaysia, to employ this technology for various applications, including engineering and infrastructure, environment, disaster and natural resource management. However, there are some technical challenges faced by technology operators and users, particularly in Malaysia, in terms of data acquisition, processing and quality control. In this paper, some of the technical challenges, i.e. mismatches between LiDAR and ground land survey data, differences between coordinates derived from the primary GPS network 2000 and the CORS station, MyGeoid and NGVD height differences, changes in topographical features, LiDAR Data management and the lack of a standard for data acquisition and quality control in Malaysia, will be discussed.

PENGGUNAAN KOMBINASI TITIK IKAT STASIUN GLOBAL IGS DAN TITIK IKAT STASIUN GPS REGIONAL YANG DIIKATKAN PADA ITRF-2008 DALAM PENDEFINISIAN STASIUN GNSS CORS GMU1

The CORS GNSS station can be used as a reference point in determining relative positions in both real time and post processing. This reference point is used for the measurement of points on the surface of the earth. In this measurement requires a high accuracy that is up to a fraction of a millimeter. In this research, GNSS CORS station which is used is GNSS CORS GMU1 which has been operated since 2009 which is located in Engineering Faculty Building of Department of Geodesy Engineering (Level Three) Universitas Gadjad Mada Yogyakarta, Indonesia. This study redefined the coordinates of GNSS CORS GMU1 using GNSS observation data for seven days from July 14, 2012 until July 20, 2012 using a combination of IGS and regional global bundle points. The tipping points of IGS global station used in this research are DGAR, GUAM, IISC, KARR, KUNM, PIMO, and TOW2. While the binding point of Regional station used is BAKO, CJPR, CDNP, CSRJ, SAMP, CBAL and CBIT. Data processing using scientific software GAMIT / GLOBK. The result of this research is 3D cartesian coordinate value from GNSS CORS GMU1 station in 2012 and its position speed. Coordinate of processing result that is X (m) = -2200206,97088 m ± 26,08 mm; Y (m) = 5924895,45433 m ± 26,30 mm; Z (m) = -855932,55993 m ± 192,51 mm. It can be seen that the standard deviation resulting from the combined processing of bundle points of Global IGS and regional stations is up to millimeter fraction. Speed position of GNSS CORS GMU1 station in 2012, that is VX = 0,02907 m / year ± 0.25410 m; Vy = 0.13655 m / year ± 0.47235 m; Vz = -0.07798 m / year ± 1.39 m.Keywords: GNSS CORS GMU1 station, GPS connectivity, GAMIT software