Abstract:The selection of a global geopotential model (GGM) for modeling the long-wavelength for geoid computation is imperative not only because of the plethora of GGMs available but more importantly because it influences the accuracy of a geoid model. In this study, we propose using the Gaussian averaging function for selecting an optimal GGM and degree and order (d/o) for the remove-compute-restore technique as a replacement for the direct comparison of terrestrial gravity anomalies and GGM anomalies, because ground data and GGM have different frequencies. Overall, EGM2008 performed better than all the tested GGMs and at an optimal d/o of 222. We verified the results by computing geoid models using Heck and Grüninger's modification and validated them against GPS/trigonometric data. The results of the validation were consistent with those of the averaging process with EGM2008 giving the smallest standard deviation of 0.457 m at d/o 222, resulting in an 8% improvement over the previous geoid model. In addition, this geoid model, the Ghanaian Gravimetric Geoid 2017 (GGG 2017) may be used to replace second-order class II leveling, with an expected error of 6.8 mm/km for baselines ranging from 20 to 225 km.

The disparity in land and food access in Ghana often overlooks the possibility of an underlying gender disparity. This paper explores and interrogates the disparity between land and food access with respect to gender and the evolution of this relationship over the years as a result of the settlement expansion and urban growth within the Adenta Municipality in Ghana. Adopting a mixed pairwise approach of combining spatial analytical tools, vulnerability indexing and resilient indicators, the paper examines the levels and rates of land accessibilities within the stream of modern cities. It assesses the land market system complexities within developing economies and attempts to address the potential threats of gender-land access gaps. The paper finally assigns weights of ranks to model the phenomenon and recommends trends that can facilitate predictions and early cautionary systems for effective urban land governance in Ghana. The paper concludes that though it is noticed that women engage in power structures on a daily basis, this both benefits and burdens them, depending on their socio-cultural status and other factors in terms of access to land and food.

Astronomic azimuths had been used for orienting old surveys in Ghana. With technological advancement and the development of simpler but accurate equipment and techniques for measurement, this has been replaced by the use of the Global Navigational Satellite System (GNSS) techniques such as the Global Positioning System(GPS). However, the use of these for azimuth determinations results in a different type of azimuth as opposed to astronomic azimuths previously used. For retracing some of those old surveys based on Astronomical coordinates, the relationship and convertibility between the different azimuths is imperative. In this exploration, the relationship and precision of both techniques were tested on various baselines located in different parts of the country. This involved the computation of Astronomic, Geodetic and Grid Azimuths between pairs of points to form several baselines. These baselines span from the Southern to the Middle belt portions of the Country where triangulations have been done, as some of these triangulation stations were Laplace stations that have both astronomic and geodetic coordinates determined for them. The results were investigated in terms of effect of using the convergence and t-T correction to convert between the set of azimuths. The results show that Geodetic Azimuths could be converted to grid coordinates and vice versa to accuracies of mean 0° 0ʹ 0.56ʺ and standard deviation ± 5.6 seconds. However, for Astronomic to Grid Azimuths, without correcting for Deflection of vertical, the conversion is accurate only to mean differences of 0° 1ʹ 25.3ʺ with standard deviation ± 0° 8ʹ 21.5ʺ. The results show the necessity of the Laplace correction for vertical deflection in astronomic azimuths in addition to the convergence and t-T correction and recommends the provision of country-wide deflection corrections.

Astronomic azimuths are bearings, which are referenced to the true north direction whereas geodetic azimuths are those referenced to a grid north direction. The difference between these two directions can be expressed through the deflection of the vertical. This deflection of the vertical refers to the difference between the normal to the geoid (Astronomic) and the normal to the ellipsoid (geodetic). The deflection of the vertical components are used to convert between astronomic and geodetic coordinates and azimuths using Laplace equations. This paper compares astronomic and geodetically derived coordinates at eight Laplace stations constituting twenty-eight baselines for which both geodetic and astronomic azimuths were derived. The comparison of azimuths shows that differences of 000°00'05.95" up to 000°23'06.93" exist between the two different versions of azimuths. These differences are not accounted for in application of the simplified Laplace equations under the assumptions made in their derivation. It is, thence, recommended that an alternative didactic approach based on rotations of three-dimensional right-handed local frames as used in Helmert’s coordinate transformations be explored for transformation between astronomic and geodetic coordinates.

Accurate and current Land Use and Land Cover (LULC) maps are important for planning purposes and to monitor the alterations to the environment mostly caused by humans’ activities. The increased utilization of land resources due to population growth have led to loss of biodiversity and urban planning issues such as flooding and pollution. This study analysed the LULC changes within the Kpeshie lagoon Basin of the Greater Accra Region of Ghana and made prediction to the year 2030. Random Forest (RF) classifier was employed to classify the LULC within the study area using Landsat image for four different time-steps (1991, 2002, 2013 and 2020). LULC change analysis was performed for consecutive years (1991 – 2002, 2002 – 2013 and 2013 – 2020) and for the entire period (1991 – 2020). Subsequently, a prediction LULC was made to the year 2030 using a combination of artificial neural network (ANN) and cellular automata (CA) simulations. The LULC classification produced 92.68%, 84.35%, 84.41% and 89.93% overall accuracies and kappa statistics of 0.87, 0.87, 0.84 and 0.91 for the time-steps respectively. Over the study period, significant LULC changes were observed, as the Kpeshie Lagoon Basin which was predominantly covered by vegetation (69.33%) in 1991 had transformed into a major built-up area (50.50%) in 2020. The spatial prediction estimated built-up to cover 60.15% in 2030, followed by bare land, 32.39%, vegetation 6.97% and waterbody 0.49%. The study revealed that LULC within the Kpeshie Lagoon Basin has been hugely impacted due to urbanization and non-enforcement of regulations.