Survey Engineering Support for Railway Alignment Design in North Central Nigeria

Railway infrastructure development in Nigeria's North Central zone, anchored by the Abuja-Kaduna standard gauge line and proposed extensions, demands precise survey engineering support to ensure alignment accuracy, safety compliance, and efficient construction execution. This study examines the survey engineering workflow supporting the preliminary and detailed design stages of a proposed railway alignment in North Central Nigeria, traversing terrain in Niger and Kogi States. The study analyses the survey programme from reconnaissance through control establishment, topographic detail survey, longitudinal profiling, cross-section surveys, and curve setting-out to the production of survey deliverables in AutoCAD Civil 3D format. Control networks are established using network RTK GNSS, with accuracy verification through independent baselines processed in GNSS solutions software. Digital terrain models derived from combined Total Station and GNSS surveys are used to optimise vertical alignment to minimise earthwork volumes while satisfying design gradient constraints. The study documents precision achieved against project specification tolerances and analyses efficiency gains from GPS-assisted over conventional traverse-based alignment survey methods. Results demonstrate that GPS-assisted survey reduces field time by over fifty percent for long alignment surveys while maintaining required accuracy standards. Recommendations address instrument type selection, quality assurance protocols, and coordination between design engineers and survey teams for railway corridor projects. Keywords: railway alignment survey, GNSS, North Central Nigeria, survey engineering, Digital Terrain Model.