Caleb Olutayo Oluwadare

For socioeconomic development, groundwater is a vital resource, especially in areas with limited water supplies. This study assesses groundwater potential zones (GWPZs) in two distinct Nigerian regions, the inland crystalline basement complex of Ile-Ife and the coastal sedimentary basin of Ilaje using integrated geospatial techniques. The novelty of this research lies in its direct comparative analysis of these two disparate hydrogeological and anthropogenic contexts, which fills a critical gap in the existing literature. The study utilized Remote Sensing, GIS, and the Analytical Hierarchy Process (AHP), including a sensitivity analysis to improve methodological robustness. For GWPZ delineation, nine key thematic layers, including geology, land use/land cover, NDWI, NDVI, drainage density, lineament density, rainfall, DEM, and slope, were processed and weighted using AHP. Significant differences were found in the results. Ilaje had a higher percentage of highly available GWPZs (6.15%) than Ile-Ife (4.00%), which was indicative of fundamental variations in hydrogeological, geomorphological, and hydrological controls. Importantly, the results highlight how these differences call for tailored management approaches; Ile-Ife's resources are being depleted by increasing urbanization, while Ilaje's potential is accompanied by serious risks of pollution and saltwater intrusion. This research demonstrates that a “one-size-fits-all’’ approach to groundwater management is untenable in diverse environments and offers fresh empirical insights for both hydrogeological theory and practical policy formulation. It is important to note that the resulting GWPZ maps, based on secondary data, should be interpreted as preliminary indicators requiring future validation through borehole logs and pump test data.

This paper advances the existing body of knowledge on the suitability of the accuracy derivable from the use of smartphones for cadastral mapping. Zenvus App software was installed on two smartphones of a different make. A set of dual-frequency GPS Promark 3 receivers and two different smartphones of different makes were used for data acquisition. Observations were carried out at the boundaries of ten parcels of land, comprising 46 boundary points. The coordinates of these points were obtained using Differential Global Positioning System (DGPS) observation in static mode and two Android smartphones (the Samsung A70 and the Tecno Spark 3 Pro). Mean score, root mean square error, and one-way analysis of variance were used to show significant differences in the equipment used. Overall, both the accuracy (mean) and precision (RMSE) were lower than those obtained by Differential GPS. A one-way analysis of variance (ANOVA) was calculated on the values of both X and Y. For X, the analysis was not significant; F (1, 45) = 0.88, p = 0.419 and for Y, the analysis was also not significant; F (1, 45) = 0.97, p = 0.383. The total RMSE shows that the coordinates of points as obtained by the Samsung smartphone (3.368) were more precise than those obtained by Tecno (4.041). However, the two smartphones (Tecno and Samsung) were less accurate than differential GPS. This implies that there is a 95% chance that the errors in the estimates are less than 6.993m (for Tecno) and 5.848m (for Samsung), respectively. The variation in the observations obtainable with smartphones affects both linear and polygon estimates. The study concluded that the magnitude of these errors is significant in cadastral survey practices and hence not suitable for use. It is recommended that further studies be carried out on the use of the Zenvus app on centimeter grade smartphones; probably this could yield a better result suitable for cadastral mapping.