Nova višinska referenčna ploskev na območju severne Alžirije, določena na podlagi modela geoida EGM2008/RTM

EGM2008/RTM based geoid model as support to a new vertical reference surface over northern part of Algeria

Author(s):

Aicha Derkaoui, Messaoud Hacini

Abstract:

In Algeria, the lack of dense and accurate gravity data has restricted the production of a precise geoid model, which serves as the means of deriving orthometric heights from GPS observations. The present paper describes the construction of a new vertical reference surface over northern part of Algeria based on EGM2008/RTM geoid model as support to earthquake and geodynamical applications. The residual terrain model (RTM) reduction has been applied for computing estimates of the omission error (high frequency signal) using the two-dimensional lateral density variations model derived from geological maps. RTM elevations are constructed as the difference between the SRTM (Shuttle Radar Topography Mission) elevation model and the DTM2006.0 spherical harmonic topographic expansion. The least-squares Collocation technique in iterative process has been used to determine the relationship between the GPS/levelling derived geoid heights and EGM2008/RTM based geoid model. According to our numerical results, this study shows that the effect on the EGM2008 based geoid model using the 2D lateral density variations model ranges from 0 to 13cm and remains significant for geoid determination with centimeter level. The comparisons of the EGM2008-only with a set of precise GPS/levelling data as references shows standard deviations of 8.5cm and 5.5cm before and after fitting using the linear trend as corrector surface, respectively. Applying RTM-based omission error estimates to EGM2008 reduced its standard deviation to 2.0 cm after fitting and therefore improves the geoid modelling by almost 63.5 %. Furthermore, the EGM2008/RTM based geoid model displays, in northern part of Algeria, an improvement in reliability than the latest local and African gravimetric geoids solutions. In second part, a correlation study between the topographical data, 2D lateral density variations model, some gravity field parameters and seismological data, was been conducted. The results of this study show a significant correlation between geoid undulation and earthquake magnitude parameter. It is around 40% for earthquakes whose magnitude exceeds 5 on the Richer scale.

Keywords:

corrector surface, EGM2008, the residual terrain model (RTM), omission error, two-dimensional lateral density variations model, seismological data

DOI: 10.15292/geodetski-vestnik.2026.01.62-82

Citation:

Aicha Derkaoui, Messaoud Hacini (2026). Nova višinska referenčna ploskev na območju severne Alžirije, določena na podlagi modela geoida EGM2008/RTM. | EGM2008/RTM based geoid model as support to a new vertical reference surface over northern part of Algeria. Geodetski vestnik, 70 (1), 62-82. DOI: 10.15292/geodetski-vestnik.2026.01.62-82