Geodetic Reference Frame Realisation and Its Implications for National Spatial Data Accuracy and Infrastructure Engineering in Nigeria

Nigeria operates with a heterogeneous geodetic reference framework legacy including the Minna Datum, the Leigon Datum in northern regions, and partial adoption of WGS84, creating position discrepancies of up to 200 metres between spatial datasets that compromise the integrity of cadastral data, engineering surveys, and national spatial infrastructure. This dissertation undertakes a comprehensive geodetic investigation of the Minna Datum transformation parameters, the current realisation accuracy of the Nigerian geodetic control network, and the implications of reference frame inconsistencies for national spatial data accuracy and critical infrastructure engineering. A nationwide GPS campaign at 143 recoverable primary control stations is conducted to derive precise ITRF2020-aligned coordinates. Helmert transformation parameters between Minna Datum and ITRF2020 are estimated using seven-parameter and ten-parameter transformation models, and residual analysis characterises the spatial pattern of datum inhomogeneity across the country's physiographic zones. Error propagation modelling quantifies the positional uncertainty introduced by reference frame ambiguities in large-scale cadastral survey products, dam construction engineering surveys, and pipeline alignment documentation. The study develops a Nigerian National Transformation Grid providing datum conversion accuracy below fifty centimetres nationally and proposes a phased geodetic infrastructure modernisation programme aligned with ITRF2020 adoption. Original contributions include the first rigorously determined nationwide Minna-ITRF transformation grid and a spatial error risk classification for existing cadastral and infrastructure surveys. Keywords: geodetic reference frame, Minna Datum, ITRF, Nigeria, transformation grid.