Geoid Validation on the Baltic Sea Using Ship-borne GNSS Data

Nordman, Maaria; Kuokkanen, Jaakko; Bilker‐Koivula, Mirjam; Koivula, Hannu; Häkli, Pasi; Lahtinen, Sonja

doi:10.1080/01490419.2018.1481160

Cited by 12 publications

(7 citation statements)

References 10 publications

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“…Unlike a geoid model on land, there are no observed geoidal heights at sea for assessing the accuracy of a given geoid model. However, a Baltic Sea geoid model (Nordman et al, 2018) has been evaluated by shipborne GPS measurements. In this case, the dynamic oceanic topography (DOT) was removed from a Baltic Sea DOT model from the ocean-tide-corrected sea surface heights from GPS to determine geoidal heights at the Baltic Sea, which were compared with the model geoidal heights.…”

Section: Assessment the Hybrid Geoid In The Taiwan Straitmentioning

confidence: 99%

The 2021 gravimetric and hybrid geoid models for Taiwan and offshore islands: Application to a seamless vertical datum

Huang¹,

Cheng²,

Hwang³

et al. 2021

Terr. Atmos. Ocean. Sci.

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We construct the 2021 gravimetric and hybrid geoid models that cover the island of Taiwan and the offshore islands of Kinmen, Matzu, Penghu, Liuqiu, Lyudao and Lanyu, where new gravity data and observed geoidal heights are available. The mean sea levels around Matzu, Penghu and Lanyu are redefined by better tidal records, resulting in new gravity anomalies. The gravity measurements from airborne, shipborne, and terrestrial gravimeters and from altimeters are combined to form a 30"×30" grid of free-air gravity anomalies. The terrain corrections are computed using updated land DEMs and ocean depths and then used to generate Faye gravity anomalies. A gravimetric geoid is created by the remove-compute-restore technique using the 1-D FFT implementation of Stokes' integration with a modified kernel. A hybrid geoid is then created using the gravimetric geoid and the observed geoidal heights. The means and the standard deviations of the differences between the model geoidal heights from the gravimetric geoid and from the observations are up to few dm and to less than 10 cm, and are reduced to few cm and 0-6 cm respectively when the model values are from the hybrid geoid.The hybrid geoid in the Taiwan Strait is assessed against the sea surface heights from the DTU18 mean sea surface model and the TOPEX-Jason series of altimeters. The hybrid geoid is one essential surface in a seamless vertical datum around Taiwan that define land elevations and ocean depths in a unified way. We discuss the potential application of the hybrid geoid to orthometric heighting in the TWVD2001 system in offshore wind farms in the Taiwan Strait.

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Section: Assessment the Hybrid Geoid In The Taiwan Straitmentioning

confidence: 99%

The 2021 gravimetric and hybrid geoid models for Taiwan and offshore islands: Application to a seamless vertical datum

Huang¹,

Cheng²,

Hwang³

et al. 2021

Terr. Atmos. Ocean. Sci.

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show abstract

“…Antenna reference points were connected to the sea level (H in Figure 3) using a total station (Figure 5a). Two antennas were used to eliminate the risks when one receiver stops working and to filter out vessel fluctuations [25,26]. Measurements were carried out on the same day of the satellite overpass; the weather was calm during all measurements (Table 2).…”

Section: In Situ Datamentioning

confidence: 99%

Validation of Copernicus Sea Level Altimetry Products in the Baltic Sea and Estonian Lakes

et al. 2020

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Multi-mission satellite altimetry (e.g., ERS, Envisat, TOPEX/Poseidon, Jason) data have enabled a synoptic-scale view of ocean variations in past decades. Since 2016, the Sentinel-3 mission has provided better spatial and temporal sampling compared to its predecessors. The Sentinel-3 Ku/C Radar Altimeter (SRAL) is one of the synthetic aperture radar altimeters (SAR Altimeter) which is more precise for coastal and lake observations. The article studies the performance of the Sentinel-3 Level-2 sea level altimetry products in the coastal areas of the Baltic Sea and on two lakes of Estonia. The Sentinel-3 data were compared with (i) collocated Global Navigation Satellite System (GNSS) ship measurements, (ii) the Estonian geoid model (EST-GEOID2017) together with sea-level anomaly corrections from the tide gauges, and (iii) collocated buoy measurements. The comparisons were carried out along seven Sentinel-3A/B tracks across the Baltic Sea and Estonian lakes in 2019. In addition, the Copernicus Marine Environment Monitoring Service (CMEMS) Level-3 sea-level products and the Nucleus for European Modelling of the Ocean (NEMO) reanalysis outcomes were compared with measurements from Estonia’s 21 tide gauges and the buoy deployed offshore. Our results showed that the uncertainty of the Sentinel-3 Level-2 altimetry product was below decimetre level for the seacoast and the selected lakes of Estonia. Results from CMEMS Level-3 altimetry products showed a correlation of 0.83 (RMSE 0.18 m) and 0.91 (RMSE 0.27 m) when compared against the tide gauge measurements and the NEMO model, respectively. The overall performance of the altimetry products was very good, except in the immediate vicinity of the coastline and for the lakes, where the accuracy was nearly three times lower than for the open sea, but still acceptably good.

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“…Antenna reference points were connected to the sea level using a total station ( Figure 5a). Two antennas were used to eliminate the risks when one receiver stops working and also to filter out vessel fluctuations [24,25]. Measurements were carried out on the same day of the satellite overpass and the weather was calm during all measurements (Table 1).…”

Section: In Situ Datamentioning

confidence: 99%

Validation of Sentinel-3 SAR Level-2 and Level-3 Products in the Baltic Sea and Estonian lakes

Liibusk¹,

Kall²,

Rikka³

et al. 2020

Preprint

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Multimission satellite altimetry (e.g. ERS, Envisat, TOPEX/Poseidon, Jason) data have enabled a synoptic view of ocean variations in the past decades, including sea-level rise and mesoscale circulations. Since 2016, the Sentinel-3 mission has provided better spatial and temporal sampling compared with its predecessors. The Sentinel-3 Ku/C Radar Altimeter (SRAL) is one of the synthetic aperture radar altimeters (SAR Altimeter) which is more precise in coastal and lake observations. In this study, we validate Sentinel-3 Level-2 products in Baltic Sea coastal areas and two lakes in Estonia. Moreover, the Copernicus Marine Environment Monitoring Service (CMEMS) Level-3 sea-level anomaly data and the Nucleus for European Modelling of the Ocean (NEMO) reanalysis model outcomes are compared with measurements from a tide gauge network. A dense in situ water level network deployed along the coast for geodetic observation was utilised to provide ground truths for validating altimetry results. Three validation methods were used for Level-2 data: (i) collocated Sentinel-3 and GNSS ship measurements; (ii) a national geoid model (EST-GEOID2017) with sea-level anomaly correction; (iii) collocated Sentinel-3 and buoy measurements. The validations were carried out in seven Sentinel-3A/B overpasses in 2019. Our results show that the uncertainty of the Sentinel-3 Level-2 altimetry product is below decimetre level on the Estonian coast and the targeted lakes. Results from CMEMS Level-3 showed a correlation of 0.8 (RMSE 0.19 m) and 0.91 (RMSE 0.27 m) when compared against tide gauge measurements and NEMO model, respectively.

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Geoid Validation on the Baltic Sea Using Ship-borne GNSS Data

Cited by 12 publications

References 10 publications

The 2021 gravimetric and hybrid geoid models for Taiwan and offshore islands: Application to a seamless vertical datum

The 2021 gravimetric and hybrid geoid models for Taiwan and offshore islands: Application to a seamless vertical datum

Validation of Copernicus Sea Level Altimetry Products in the Baltic Sea and Estonian Lakes

Validation of Sentinel-3 SAR Level-2 and Level-3 Products in the Baltic Sea and Estonian lakes

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