Analysis of Elevation Models for Nigerian 2D Cadastre Height Determination

Abstract

In Nigeria, the spatial requirements of cadastral map for the purposes of land registration are based on 2D planimetric boundary coordinates without consideration for the elevation component of geometric space. Whereas, recent development in technology and practises in many countries requires the inclusion of elevation component into the cadastre. The specific objectives of this study are to determine elevation values for existing 2D cadastre of the study area from different data sources and to analyze those elevation values using statistical means. Data were sourced from both primary and secondary sources; secondary data include a 30m by 30m resolution Global Digital Elevation Model (GDEM), Shuttle Radar Topographic Mission Data (SRTM), 1:50,000 topographic map and existing Digital Elevation Model (DEM) of the study area. Ten ground control points were established at 250m grid with Global Positioning System in differential mode and elevation data were obtained accordingly. Elevation values of selected existing planimetric controls (33) were also determined from adopted data sources and were compared using both the standard deviation and the Root Mean Square Error (RMSE). The vertical accuracy obtained from Topographic map data, existing DTM, ASTER data and SRTM data were ± 1.860, ± 3.450, ± 5.309 and ±4.573 respectively relative to elevation values obtained from GPS observation of corresponding selected existing 2D planimetric controls. The degree of association between elevation values obtained from adopted data sources was strong and positive as shown from the regression analysis. The study established that only topographic map elevation data would presently fit GPS elevation data for 3D cadastre implementation for the study.