The determination of Thailand Geoid Model 2017 (TGM2017) from airborne and terrestrial gravimetry

Dumrongchai, Puttipol; Srimanee, Chawis; Duangdee, Nuttanon; Bairaksa, Jittrakorn

doi:10.3319/tao.2021.08.23.01

Cited by 3 publications

(1 citation statement)

References 16 publications

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“…Similary, Australia has created its own geoid, known as the AUSGeoid, which is accurate to within 4-8 cm. Australian height datum (AHD) can be computed directly from the GNSS and AUSGeoid of accuracy of 6-13 cm (Intergovernmental Committee on Surveying and Mapping (ICSM), 2021) Additionally, Thailand's gravimetric geoid model 2017 (THAIG17) has rmse of 4.9 cm, which results in accurate heights of at least 10 cm accuracy level or better (Dumrongchai et al, 2021). However, the study used the geoid (geoid 2021) to extract the geoid undulation has reported accuracy of only about 8 cm in the sagarmatha region and 4 cm in the current study area.…”

Section: Precision Of Existing Geoidmentioning

confidence: 99%

Can GNSS Derived Height Replace Levelling Height? - A Case of Low-Land of Nepal

KC¹,

Bhandari²,

Upadhyaya³

et al. 2023

J. Geoinformatics, Nep.

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Orthometric height is the generally adopted type of height worldwide and in geomatics community. Precise levelling has been the method of obtaining orthometric height in past for most of the country, so as the Nepal. However, due to wide usage of Global Navigation Satellite System (GNSS), the alternative approach of combining GNSS derived ellipsoidal height with geoid undulation to get GNSS derived orthometric height, has been used extensively. In Nepal, this technique was officially adopted in 2020 for Everest height measurement and understood as the efficient way to comply with levelling height. In this study, GNSS surveying was conducted on 15 stations located at the lowland region of Nepal and orthometric heights were obtained from GNSS and geoid method. When compared GNSS derived orthometric height with precise levelling height, the difference remained within threshold of 5cm for majority of observation stations. However, these differences are not sufficient to support the standards set for the third order levelling by Survey Department (SD). The accuracy of GNSS derived orthometric height can be significantly affected by various environment and existing resources such as existing accuracy of geoid, nature of precise levelling height. Considering the revisit upon these conditions, we expect GNSS-levelling as a strong alternative to time consuming, tedious, and costly precise levelling which is most suitable method of obtaining orthometric height in lowland topography at a precision less than 4 cm.

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Section: Precision Of Existing Geoidmentioning

confidence: 99%

Can GNSS Derived Height Replace Levelling Height? - A Case of Low-Land of Nepal

KC¹,

Bhandari²,

Upadhyaya³

et al. 2023

J. Geoinformatics, Nep.

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Geoid Undulation Model as Vertical Reference in Indonesia

Pahlevi,

Syafarianty,

Susilo

et al. 2024

Sci Data

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Indonesia released a new regional geoid model in 2020—the Indonesian Geoid 2020 (INAGEOID2020). It covers the Indonesian region with a spatial resolution of 0.01 × 0.01 degree with the unit in meters. The model was generated through a series of data and computations. Three components of gravity data, i.e., the observed free-air anomaly, the long-wave from the global geoid model, and the short-wave from the terrain model, were employed. The computation was performed using the Remove-Compute-Restore technique with the Fast Fourier Transformation approach. The output was then fitted to the geoid at tide stations by adding a fitting plane to the geoid model. The fitting plane was constructed based on the difference between the geoid model and each tide gauge benchmark. The final geoid model was evaluated by comparing the model with the reference data. Based on quality metrics, the accuracy of INAGEOID2020 varied between 6 cm to 29 cm. Any interested user can use this gridded geoid model to convert geodetic to orthometric heights and vice versa.

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

Dumrongchai

Patsadutarn

Satirapod

2022

Journal of Applied Geodesy

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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.

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The determination of Thailand Geoid Model 2017 (TGM2017) from airborne and terrestrial gravimetry

Cited by 3 publications

References 16 publications

Can GNSS Derived Height Replace Levelling Height? - A Case of Low-Land of Nepal

Can GNSS Derived Height Replace Levelling Height? - A Case of Low-Land of Nepal

Geoid Undulation Model as Vertical Reference in Indonesia

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

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