UNIFIED DIGITAL ELEVATION, MODEL DEVELOPMENT FOR ERELU RESERVOIR AND ITS CATCHMENT AREA, OYO WEST LOCAL GOVERNMENT AREA, OYO STATE
Abstract
ABSTRACT
This research focuses on the development of a Unified Digital Elevation Model (UDEM) for the
Erelu Reservoir and its catchment area, located in Oyo State, Nigeria. The study integrates
terrestrial Global Navigation Satellite System (GNSS) data and bathymetric measurements
obtained from a Single Beam Echo Sounder (SBES) to produce a seamless digital terrain
representation encompassing both land and underwater surfaces.
A systematic workflow was implemented, beginning with reconnaissance, instrument testing and
calibration, followed by topographic and bathymetric data acquisition, preprocessing,
integration, interpolation, and model validation. Field observations were conducted using dual-
frequency UniStrong G970II GNSS receivers operating in Real-Time Kinematic (RTK) mode,
while the SBES was deployed for depth sounding with continuous GPS referencing. Data were
processed using ArcGIS 10.7.1, Surfer 16, Global Mapper 24, and Microsoft Excel, employing
raster interpolation techniques for surface generation. Both datasets were referenced to the
Minna Datum (Clarke 1880 Ellipsoid, UTM Zone 31N) to ensure spatial consistency.
The resulting UDEM achieved a spatial resolution and demonstrated an RMSE accuracy of
±0.30m, signifying high vertical precision relative to IHO and SURCON standards. Derived
products including contour, slope, aspect, hillshade, and 3D terrain maps revealed detailed
morphometric characteristics of the reservoir basin, identifying sedimentation zones,
hydrological flow directions, and erosional features. The unified model proved superior to global
DEMs in representing terrain continuity, making it a valuable dataset for hydrological modelling,
reservoir sedimentation assessment, flood risk analysis, and water resource management.
The study concludes that the integration of locally acquired GNSS and bathymetric datasets
significantly enhances the spatial accuracy and interpretive value of elevation models. It
recommends periodic topo-bathymetric surveys, institutional capacity building in geospatial data
integration, and the establishment of centralized geospatial repositories for sustainable reservoir
and watershed management in Nigeria
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