Unfired compressed earth blocks stabilized with lime and reinforced with agro-residual fibers are promising resource-efficient materials for tropical construction. This study investigates the mechanical and thermophysical performance of compressed earth blocks from a clayey soil (Dibang, Cameroon) stabilized with 12% quicklime and reinforced with coconut mesocarp (NC) or oil-palm mesocarp (NP) fibers. Mechanical tests showed no statistically significant effect of fiber content on dry compressive strength (p > 0.05), although the highest mean values were 7.35 MPa for NP at 2.5% fiber and 7.24 MPa for NC at 1.5%. Flexural strength reached 5.98 MPa for NC and 5.83 MPa for NP at 2.5% fiber, with a statistically significant dosage effect for NP (p < 0.05). Thermal conductivity decreased with increasing fiber content, reaching 0.691 W·m⁻¹·K⁻¹ for NC and 0.712 W·m⁻¹·K⁻¹ for NP at 3% fiber, the lowest values measured within the investigated thermal-characterization range. These properties were used to parameterize a three-dimensional transient finite-element heat-conduction model of an 80 × 25 × 15 mm specimen under a 10 K gradient. The finite-element solution was numerically verified against an independently implemented finite-difference solver and a closed-form analytical solution (RMSE < 0.11 K; R² > 0.998). The fitted hot-strip parameters were independently validated against experimentally acquired thermograms for 16 formulations (R² ≥ 0.986). Overall, coconut fibers showed higher intrinsic tensile properties and slightly lower conductivity than oil-palm fibers, with moderate fiber contents offering the most favorable mechanical response. The results support the potential of these fiber-reinforced earth blocks for tropical building-envelope applications.

This study analyzes satellite-derived gravimetric data from the XGM 2016 model to investigate the tectonic and structural framework of central Cameroon and to evaluate potential links with seismic hazards and vulnerability. Regional and residual components of the Bouguer anomaly were separated using 2D spectral analysis and a cosine filter with cut-off frequencies between 0.015 and 0.5 rad/ km, allowing the isolation of local signatures relevant for structural interpretation. A visual inspection of the residual gravimetric anomalies revealed various amplitude variations with abrupt changes, reflecting local heterogeneities in subsurface mass distribution. Advanced edge detection techniques, especially the Normalized Edge Detection (NED) and Fast Sigmoid Edge Detection (FSED) proved effective in delineating geological contacts and fault-related structures, supporting the interpretation of major subsurface boundaries. Euler deconvolution (SI = 1) constrained the depth of several lineaments, with most sources located between 13 and 18 km. Forward 2.5D gravity modeling, constrained by regional geology and seismic velocity models, suggests crustal heterogeneities involving possible gneissic and syenitic intrusions, localized upper-crustal thickening, and zones of deformation near major tectonic boundaries. These interpretations remain consistent with previously documented structures, including the Sanaga Shear Zone (SSZ), Central Cameroon Shear Zone (CCSZ), and the northern margin of the Congo Craton (CC). Finally, the spatial comparison between gravimetric lineaments, seismic events, population density, and road infrastructure highlights areas of potential vulnerability. The northern margin of the CC and the Cameroon Volcanic Line (CVL) emerge as priority zones, where crustal structures coincide with recorded earthquakes and highly urbanized, infrastructure-dependent regions. These results underscore the importance of integrated gravimetric, geological, and seismological approaches for assessing tectonic instability and seismic risk in Central Africa. (c) 2025 COSPAR. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

The dynamics of a composite consisting of the nonlinear multilayer beam structure, interacting through elastic intermediate layers, under mobile point loading is investigated. This study finds a direct application in transport engineering technologies, more precisely in railways, where the moving point load is the train, and the multilayer beam, the rails interacting with the ballast, the foundation and base layers. From the Lagrange formulations, the system of damping partial differential equations of the model is found, and by considering the non-dissipative case with weak nonlinearity and constant charge they are used to find the eigen modes and the natural vibration frequencies of the system. Then the dissipative case with nonlinearity is studied, with a particular attention carried on the temporal part, which is reduced to a system of coupled nonlinear differential equations, where the first line is forced. This system of equation is used to determine the equilibrium points, after which they are subsequently solved analytically through the multiple time scale method for harmonic resonance case, showing the formation of hysteresis more and more complex as the number of cells increases. The coupled nonlinear equations of the system is next solved numerically, with the transition of the system towards chaos analyzed through the bifurcation diagram and the maximum Lyapunov exponent, which show strong sensitivity to the coupling parameter λ2 as well as the system frequency. The results show for N = 2 and for some parameters the periodic behavior and the crisis for ω = 0.5. When the frequency is low; that is ω = 0.05 the chaotic band is considerably reduced, chaos appearing around the nonlinearity parameter γ2 = 0.5 and also for γ2 > 0.85. The time trace shows chaotic pulses and bursting type behavior, for some choices of the coupling parameter. The synchronization curves are also plotted and it is shown that q2 doesn’t synchronizes with q1 for some frequencies, while for others parameters, they synchronize, but fairly. For N = 3, the dynamics is more complex and the time traces plots show regular impulse for ω = 0.5 and bursting for weak frequency, ω = 0.05.

The main objective of this study is to compare the physicochemical and thermo-mechanical properties of two types of plant fibers (coconut and oil palm), as well as their thermal behavior when incorporated into stabilized compressed earth blocks (SCEBs). The fibers were chemically treated with a 2 % sodium hydroxide solution at 70 °C and characterized in terms of physical, chemical, thermal, and mechanical properties. The results revealed significant differences depending on the fiber type. Water absorption was found to be 75 % for coconut fibers and 47 % for oil palm fibers. The densities were 1.15 and 1.06 g/cm³ respectively, while the crystallinity index was 63.37 % for coconut fibers and 60.25 % for oil palm fibers. The microfibril angle (MFA), measured by X-ray diffraction, was 19.80° ± 1.57 for coconut fibers and 20.76° ± 0.76 for oil palm fibers, indicating a more favorable alignment for mechanical performance in coconut fibers. Moisture content was 9.3 % and 9.1 % for coconut and palm fibers respectively. FTIR analysis confirmed the presence of functional groups such as cellulose, hemicellulose, lignin, pectin, and water-soluble sugars. The average fiber length was 182.44 mm for coconut fibers and 25.33 mm for palm fibers, with corresponding average diameters of 0.26 mm and 0.18 mm. Thermogravimetric analysis identified the degradation temperatures of the main lignocellulosic components. Mechanical tests showed that coconut fibers exhibited superior performance, with an average tensile strength of 72.13 MPa, a Young’s modulus of 4.52 GPa, and an elongation at break of 1.61 %. In contrast, oil palm fibers showed a tensile strength of 27.07 MPa, a modulus of 2.68 GPa, and an elongation of 0.89 %. Thermophysical characterization using an asymmetric hot plate setup allowed for the measurement of thermal conductivity, effusivity, diffusivity, and heat capacity. The results demonstrated a significant improvement in the thermal insulation performance of samples containing lime and plant fibers, making them suitable for sustainable housing construction in tropical climates.

This study aims to investigate the improvement of the hydrophilic behavior of bamboo fibers extracted by the "Improved Hydrophilic Extraction Method" (IHEM) (with 3% soda) and treated by acetylation. A sample of Bambusa vulgaris fibers obtained. Three categories of fibers’s structure were exploded in composite sample, molded in same condition. Each categories of fibers’s structure has composite with treated fibers and other with untreated fibers, and was subjected to a cycle of wetting/drying/wetting test for five days duration under. It resulted that the surface area of the fibers was smoothed by 3.57% and the density was reduced by 70.08%. The elastic properties of the accessible fiber, such as Young's modulus read 14777.75 MPa while the breaking stress yieds 39.21 MPa. Water absorption decreased by 20% to 37% after 48 hours of quenching, despite the temperature variation. The comparison of water saturation mass (DM), moisture mass after drying (MT) and mass variation of the composite substituted in water after soaking (ΔM), showed that the increase in the rate of treated fibers reduces the hydrophilic character of the composite which becomes completely hydrophobic to 15%, and that the damage caused to the composite by the hydrophilic effect also becomes less important.

Road transport is one of the main causes of air pollution around the world. Nowadays, the notion of sustainable development is one of the major pillars for a healthy environment. However, faced with its major challenges, it is more than necessary and important to understand a set of elements which contribute to better understanding the level of planning for sustainable road transport. This study aims to estimate energy demand and greenhouse gas emissions, namely from road transport, for the city of Douala in Cameroon from 2010 to 2035. In order to achieve our objective, we used the Long range Energy Alternative Planning (LEAP) model. Based on the LEAP model, the estimates were evaluated based on three scenarios Business As Usual (BAU), Energy Optimization and Mitigation (EOM) and Sustainability Mobility (SM). The aim of this work was to identify suitable potential policies with a view to reducing energy consumption and emissions carbon dioxide () for road transport in Douala. The results tell us that the EOM and SM scenarios have advantages over the BAU scenario with the SM scenario being more optimistic than the other two scenarios. In addition, the SM scenario has a growth rate of 87.408 % in energy demand smaller than the other two scenarios BAU and EOM respectively 151.598 % and 132.073 %. We also note that the SM scenario contributed to a reduction of 60.661 kilo ton emissions of less than the BAU scenario. At present, with a view to reducing energy consumption and reducing carbon emissions, road vehicles in circulation in the city of Douala should emphasize structural optimization measures through the use of clean energy by promoting the use of biofuels in mass transport, eliminating old cars and finally considering improving energy efficiency through the implementation of technological development in the automobile sector. Policy makers must take this study into consideration in order to better integrate the notion of energy sustainable road transport.

Abstract The aim of this study is to study the hygrothermal behavior of bamboo fibers extracted by the alkaline method (3% soda) and treated with acetylation for potential use in house and fence siding. 10 g of 5-year-old fibers of "bambusa vulgaris" was soaked in 400 ml of glacial acetic acid, with 50 ml of catalyst (sulphuric acid) for 4 h at 30 ° C. After extraction by the « Improved Hydrophilic Extraction Method » and treatment in the laboratory, the diameter and lateral area observed with a magnification of 2, a 16x eyepiece and a 40x lens using an optical microscope equipped with a Balow lens, show that the fibers were smoothed to more than 3.57%; The absorption studied over three temperature ranges (30 oC, 50 oC and 70 oC), shows that it has decreased by about 20% and can grow with temperature to the limit of 37% after 48 hours of quenching; The composite was manufactured in three types of structure; increasing the rate of treated fibers reduces the hydrophilic character of the composite, it becomes completely hydrophobic from 15%; Increasing the level of treated fibres reduces the hydrophilic character of the composite; and damage to the composite due to the hydrophilic effect of the treated bamboo fibers is less significant..

Based on potential field data, anomalies derived from the EIGEN6C4 satellite model were used to interpret various structural features of the coastal plain, Southwest Cameroon volcanic line, northwestern margin of Congo Craton (CC) and southern extension of Pan-African belt. Since building a global comprehension of unknown phenomena about Earth’s materials is of high relevance given the tectonic complexities of the investigated area, some edge enhancement techniques were applied to the gravimetric data. After generating the Bouguer anomalies, a cosine filter was used to provide the residual data set that should characterize the gravity effect arising from superficial density sources, and finally, some amplitude and phase-based edge detection methods were used to interpret the computed Bouguer and residual data. The results of this research work have demonstrated that the enhanced horizontal gradient amplitude and fast sigmoid edge detector (FSED) filters could detect density boundaries more successfully than the other filters tested. The structural map generated by FSED revealed that the delineated lineaments are oriented NW–SE, NE–SW, N–S and NNE–SSW. In addition, important tectonic features such as Central Cameroon, Kribi–Campo and Sanaga shear zones are indicative of the effectiveness of this methodological approach and the CC limit was better highlighted in this research work. In general, the lineament map enhances the knowledge of the structural setting of the Douala Kribi–Campo sedimentary basin as well as unexposed fracture zones that may have caused seismic events in recent years.

The city of Douala in Cameroon is facing great challenges in terms of its demographic growth, economic development and urbanization, especially in relation to environmental and economic factors. However, there has been significant growth in its road transport sector, which has led to an excessive demand for the consumption of fossil fuels and an increase in greenhouse gas emissions in recent decades within this sector. However, no concrete policy has yet been put in place to improve the energy efficiency of the transport sector. This work aims to identify the driving factors and determine their contributions to the variation in energy consumption. In this study, a decomposition analysis via the Logarithmic Mean Divisia Index (LMDI) method is used for the period of 2010–2019 to quantify the respective effects of the driving factors on the variation in energy consumption. Based on the study of the literature, we classified four main driving factors in the road transport sector that contributes to the total variation in energy consumption, such as vehicle energy intensity, vehicle intensity, gross domestic product (GDP) by capita, and population scale, with each contributing 13.06%, 31.30%, 12.85%, and 42.76%, respectively. In particular, we note that the energy intensity coefficient of the vehicles from 2013 to 2016 and that of the intensity of the vehicles coefficient from 2010 to 2011 and 2012 to 2013 are the two factors that have, nevertheless, led to a slight decrease in the variation in energy consumption. This implies that an improvement in these two factors would contribute to enhancing the energy efficiency of the road transport sector of the city of Douala. It will therefore be necessary to put in place several energy-saving strategies that would lead to a rationalization of energy consumption in order to reduce greenhouse gas emissions by road transports. Policymakers should take this study into account to achieve a balance between energy consumption and economic growth to better integrate the notion of sustainable road transport.

In this study, XGM2019e_2159 global gravitational model data are used to investigate the intracrustal structure beneath Cameroon. The work focuses on the mantle region that promoted the formation of the Cameroon Volcanic Line (CVL) and above all, appreciates the geodynamic interaction between these two particular geological entities. The approach is based on the use of digital filters for qualitative and quantitative interpretations. The data were first processed using the upward continuation filter that reveals several zones of gravity gradients, which are persistent at various depths and that can be interpreted as the vertical extension of major geological feature limits. The (2D) analysis of the frequency spectrum of the global gravity model anomalies (XGM2019e_2159) was performed to estimate the crustal thickness of the aligned volcanic regions located in Cameroon and Congo Craton (CC). The use of 2D1/2 modelling applied on 5 profiles reveals the lateral and vertical extension of the discordance of geological structures. The presence of a mafic layer with thicknesses ranging between 6 and 22 km is persistent beneath the Kribi-Campo area, the Congo Craton and the Pan-African chain. Models also suggest a crustal thinning process at the northern border of Congo Craton which may have provoked the sliding of some fragments of the crust in the Pan-African domain migrating towards the CVL. The results obtained also reveal the identity of a complex and multi-fractured tectonic context and that the CVL and the CC are not only of mantle origin but also have a mantle interconnection.

In this study, Douala, Cameroon was used as a case study to analyze the characteristics of sustainable energy for road transport from 2010 to 2019. Douala, being the national capital and entry point to Central Africa, served as a major hub for the movement of people and goods. However, the road transport sector was plagued by a number of problems, including traffic congestion, the use of fossil fuels, air pollution, and global warming associated with road traffic. The objective of this work was to evaluate a set of indicators that would allow monitoring the evolution of trends in the interactions between the energy component and sustainable development. The DPSIR (Driving Force, Pressure, State, Impact, and Response) model was used to select a set of indicators. According to the results, the energy intensity of the fuel used for transport decreased from 9.93 to 15.9 toe/M€. This increase in energy intensity reflected the energy-intensive nature of the road industry. Additionally, from 2010 to 2019, the energy efficiency of road transport vehicles in the city of Douala fluctuated between 20 and 22%. This indicates a significant potential for improving energy efficiency. Therefore, decision-makers need to implement sustainable transport planning to address these issues.

EIGEN 6C4 gravity anomalies are interpreted to determine the lateral and vertical variations in the crust and upper mantle structure and their influence on the isostasy of the coastal plain, transition zone between the Congo Craton (CC), the Pan-African Belt (PAB), and adjacent areas. The regional gravity anomalies have been inverted in an attempt to provide a Moho depth map. The inversion process was based on the Parker-Oldenburg method with a density contrast of 0.55 g/cm(3) and an average depth reference of 39 km. In addition, various tests have been performed to validate the resulting Moho model and estimate the efficiency of the 3D gravity inversion by varying the density contrast for a fixed Moho reference depth. Inversion results reveal that the Moho depths generally agree with those obtained from previous geophysical studies. The computation of the isostatic models using the ETOPO1 digital elevation model (DEM) and its comparison with the Moho models obtained from gravity induce the following main conclusions: (1) an overcompensated crust beneath the coastal plain and the Yaounde Domain, (2) the crust beneath areas located in the southern end of the Adamawa-Yade Domain is thin and undercompensated, and (3) main volcanoes of the Southwestern Cameroon Volcanic Line (CVL) are isostatically undercompensated. This study also revealed that the local isostatic compensation law is not satisfied for most of the tectonic provinces of the study area, and we suggest alternative tectonic mechanisms to support topography below these tectonic features. Additionally, most seismic events (M > 3.5) occurred in areas marked by abrupt changes in compensation amplitude. Thus, we concluded from this study that the northern limit of the CC, the Mount Cameroon, and its surroundings are tectonic extension areas that may play a crucial role in the occurrence of future earthquakes.

The cartography of lineaments across a territory can be optimized using geophysical potential field data. In this study, land gravity and EMAG2 (Earth Magnetic Anomaly Grid) data were simultaneously used to identify and characterize the major lineaments that spread across Cameroon. The data were filtered using a multi-scale approach including horizontal and vertical gradient analyses. The Euler Deconvolution method was later applied to the filtered data to estimate the extension and depth of the identified lineaments. Results show that the main lineaments across Cameroon are laterally extended with a dominant N45°E orientation. Some of these lineaments correlated well with the geographical location of some known major tectonic structures found across the country. The depth of these lineaments varies between 1 and 35 km. Some of the identified faults are still active as their location correlated with the location of some recent earthquakes that occurred in Cameroon. This work, therefore, highlights some hidden tectonic features which knowledge generally precedes exploration for subsurface resources. Graphical Abstract

The increasing use of composites reinforced with vegetable fibers in the industrial field poses a serious problem of the reliability of the structures produced. For us, this credibility can be ensured when developing the composite, by a judicious choice of matrix and reinforcement, a choice leading to obtaining a material having acceptable mechanical and physicochemical characteristics. The main objective of this study is to characterize a composite material with a clay matrix reinforced with coconut and palm nut fibers. To achieve this objective, we first opted for the implementation of this composite by contact molding, at different fiber percentages (2.5%, 5%, 7.5%, and 10%), and we then subjected our specimens to mechanical tests (three-point bending and compression). The mechanical characterization allowed us to have a Young’s modulus in compression varying between 63.82 and 68.82 MPa for palm nut fibers and from 68.28 to 74.43 MPa for coconut fibers (this allows us to note that our coconut fibers make the material rigid in compression), and a Young’s modulus in bending varying between 5.71 and 6.51 MPa for palm nut fibers and from 6.50 to 6.525 MPa for coconut fibers (this allows us to see that our coconut fibers make the material rigid in bending). The results also show that the rate of water absorption of the composite increases with the increase in the fiber content, which is explained in particular by the fact that the fibers of plant origin are hydrophilic and have a porous character; therefore, they absorb water. This study also shows that there is a reduction in the density of the fiber composite with increasing fiber content.

The marine gravity field is vital for mapping various submarine geological and tectonic structures, also for computation of high-resolution gravimetric geoid. This study aims to evaluate the accuracy of two latest high-resolution marine gravity models derived from satellite altimetry (DTU17 and SSv27.1) using shipborne gravity data and to pruduce high-precision gravity field over the Gulf of Guinea. The gross-errors affecting the shipborne gravity data have been removed by cross-validation technique to ensure better evaluation of gravity field models. The standard deviation σ of the differences between the measured and model gravity data drops from 9.96 mGal before the cross-validation to 6.28 mGal after this process. The comparison between the DTU17 and SSv27.1 gravity field models has been done in order to detect significant differences between them. The differences between the two models are quite small with a mean of 1.73 mGal and σ of 6.55 mGal. The discrepancies between them are found around coastal areas and along islands. This shows the poor accuracy of satellite altimetry near coastal areas. Afterwards, the accuracy of each marine gravity field models was evaluated using shipborne gravity data free of gross-errors. The SSv27.1 model fits better to the shipborne gravity data with a mean of −4.88 mGal and σ of 7.18 mGal. Hence, the SSv27.1 model has a better performance than the DTU17 model on the Gulf of Guinea. Finally, we used the least-squares collocation technique associated to the Markov model of second-order covariance to combine the SSv27.1 model with the shipborne gravity data. We produced here a marine gravity field of good accuracy around the Gulf of Guinea with no data gaps. The precision of this combined gravity field is estimated to be 5.54 mGal with a spatial resolution of 1 arc-minute.

Interpolation methods are frequently used during gravity surveys to improve the coverage of gravity data, particularly in areas where data is scarce and sparse. This is a region which, due to its isolation, has only benefited from a single gravimetric survey campaign, with very little data collected, thus constituting a real obstacle to a geophysical study, even though it has real mining potential (Claude et al. in Adv Remote Sens 10:1, 2021). The ANN (Artificial Neural Network) method is a recent interpolation method applied to gravimetry that imitates the functioning of the biological neural network of the human brain. This paper aims to confirm the effectiveness of the ANN method on the densification of gravity data in the Lom-Pangar region where the distribution of gravity data is particularly weak and irregularly distributed. The Matlab program allowed us to build an ANN architecture with an input layer, a hidden layer, and an output layer. Statistical analysis and regression curves allow us to evaluate the degree of similarity between the Bouguer gravity data obtained in-situ and that calculated by the artificial neural network. In this study, good results were obtained using these statistical parameters: the correlation coefficient (R2 = 0.9811), the root mean square error (RMSE = 0.0804) and the mean bias error (MBE = 0.0003). Even better, these statistical parameters are significantly better compared to those obtained via other classical interpolation methods. The observed Bouguer gravity data and those obtained by the ANN method show relevant similarities, so we obtained a map of Bouguer that showed more pronounced anomalies, with more pronounced shapes and contours; reflecting specific and deeper geological structures compared to those obtained in this region using other methods. The ANN method is therefore appropriate for interpolating gravity data and could be useful in improving the gravity coverage of the Lom-Pangar region and other regions of Cameroon and indeed any region of the world that may experience similar difficulties.

The electromechanical system consisting of an electrical part which is the forced Vander Pol oscillator coupled magnetically to a mechanical part is investigated. The mechanical part is the network consisting of discontinuous elastically coupled system oscillators with strong irrational nonlinearities in which the damping is introduced. This coupled electromechanical system is connected at the output to movable sieve for the industrial applications, it can be used for the filtering of different types of building materials. By using then the Newton's second law and Kirchhoff's law, the set of model damped equations governing the dynamics of the system are established. These set of equations have strong irrational nonlinearities, with smooth or discontinuous characteristics depending just to the inclination angles of strings. Then the resonance phenomenon showing the appearing of hysteresis as the frequency shift increases is found and is more and more complex as the cell number increases. By solving numerically the set of equations of the system, one obtains the oscillatory bursting in the electrical part, and impulse bursting in the mechanical part, with their widths which decrease as the excitation frequency increases. It is also found that chaotic bursting appears in the mechanical part when the electric part exhibits periodic bursting oscillations.(c) 2022 Elsevier Ltd. All rights reserved.

The classical Exner model coupled with a bed-load sediment flux formula is widely used to describe the morphodynamics of coastal environments. However, the main drawbacks of this model are (i) Lack of robustness, (ii) Lack of differentiation between sediment and fluid velocities, and (iii) Generation of instabilities when the interactions between sediment and fluid flow become more important. Moreover, Exner's model does not allow us to know with which characteristic velocity the bottom is moving. This set of drawbacks weakens the effectiveness of most sediment transport models proposed in the literature, particularly the Exner model. In this work, we reformulate the bed-load equation and we propose a new averaged sediment transport model for application in coastal or estuarine environments. The proposed model incorporates phase shift effects into the bed-load equation. The bedform's characteristic velocity, sediment, and fluid velocity are differentiated. We developed a new first-order, well-balanced, positivity-preserving, path-preserving, and central wind (WBPP-PCCU) scheme to solve the proposed hyperbolic sediment transport model (HSTM). We used the Averaging Essentially Non-Oscillatory (AENO) reconstruction coupled with the third-order Runge-Kutta Semi-Implicit (SI-RK3) method to achieve second-order accuracy. The balance and positivity of the water depth properties were proven. In this work, a resonance condition is proposed. The model facilitates the application of several other schemes such as Roe, HLLC, HLLEM, PVM (polynomial viscosity matrix), RVM (rational viscosity matrix), which require the diagonalization of the Jacobian matrix. The accuracy, robustness, positivity preservation, and equilibrium properties of the resulting model are evaluated using a series of carefully selected test cases. The proposed model provides an excellent ability to simulate sediment transport in a wide range of coastal environments.

In this work, the principal aim is to evaluate some recent GGMs on the Gulf of Guinea region using shipborne free-air gravity data. Two types of GGMs are evaluated in this study: combined models (EGM2008, EIGEN-6C4, GECO, SGG-UGM-1, GOCO05C and XGM2016) and satellite-only models (DIR_R5, ITU_GGC16, SPW_R5, TIM_R5, GGM05G and NULP_02S). The comparisons between these GGMs and the preliminary filtered shipborne gravity data were performed before and after the Spectral Enhancement Method (SEM). The statistical results have shown that the combined models have a better performance than the satellite-only models. Before and after SEM, we note that the EGM2008 model presents the best statistical results compared to the shipborne gravity anomalies (RMS and SD values respectively changes from 3.87 to 3.55 mGal and from 3.57 to 3.32 mGal). However, the DIR_R5 model is the best of the satellite-only GGMs of this study.