GOCE Downward Continuation to the Earth’s Surface and Improvements to Local Geoid Modeling by FFT and LSC

GOCE Downward Continuation to the Earth’s Surface and Improvements to Local Geoid Modeling by FFT and LSC

One of the main applications of the gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite data is their combination with local gravity anomalies for geoid and gravity field modeling purposes. The aim of the present paper was the determination of an improved geoid model for the w...

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Bibliographic Details
Published in:Remote sensing (Basel, Switzerland) Vol. 15; no. 4; p. 991
Main Authors: Natsiopoulos, Dimitrios A., Mamagiannou, Elisavet G., Pitenis, Eleftherios A., Vergos, Georgios S., Tziavos, Ilias N.
Format: Journal Article
Language:English
Published: Basel MDPI AG 01-02-2023
Subjects:
Altitude
Analysis
downward continuation
Earth surface
Earth’s surface
Fast Fourier transformations
Fourier transforms
Geoids
Geopotential
Global navigation satellite system
GOCE
GOCE (experiment)
Gravitational fields
Gravity
Gravity anomalies
gravity gradient
Iterative methods
Leveling
mean orbit
Modelling
Monte Carlo annihilation method
Monte Carlo simulation
Mountain regions
Mountainous areas
Ocean circulation
Ocean currents
Remote sensing
Satellites
Simulated annealing
Software
System theory
Water circulation
Greece
Germany
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Summary:One of the main applications of the gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite data is their combination with local gravity anomalies for geoid and gravity field modeling purposes. The aim of the present paper was the determination of an improved geoid model for the wider Hellenic area, using original GOCE SGG data filtered to retain only useful signals inside the measurement bandwidth (MBW) of the satellite. The filtered SGGs, originally at the satellite altitude, were projected to a mean orbit (MO) and then downward continued to the Earth’s surface (ES) in order to be combined with local gravity anomalies. For the projection to an MO, grids of disturbing gravity gradients from a global geopotential model (GGM) were used, computed per 1 km from the maximum satellite altitude to that of the MO. The downward continuation process was then undertaken using an iterative Monte Carlo (MC) simulated annealing method with GGM gravity anomalies on the ES used as ground truth data. The final geoid model over the wider Hellenic area was estimated, employing the remove–compute–restore method and both Fast Fourier Transform (FFT) and Least Squares Collocation (LSC). Gravity-only, GOCE-only and combined models using local gravity and GOCE data were determined and evaluation of the results was carried out against available GNSS/levelling data in the study area. From the results achieved, it was concluded that even when FFT is used, so that a combined grid of local gravity and GOCE data is used, improvements to the differences regarding GNSS/levelling data by 14.53% to 27.78% can be achieved. The geoid determination with LSC was focused on three different areas over Greece, with different characteristics in the topography and gravity variability. From these results, improvements from 14.73%, for the well-surveyed local data of Thessaly, to 32.88%, over the mountainous area of Pindos, and 57.10% for the island of Crete for 57.10% were found.
ISSN:2072-4292
2072-4292
DOI:10.3390/rs15040991