Attributes of Topographic Mapping of a Fast Urbanising Area in Nigeria, Using Remote Sensing and GIS

Abstract

Aims: To produce an updated 1:25,000 topographic map of Anyigba through the application of geospatial technologies – GIS techniques, Remote Sensing data, GPS and other ancillary hardware and software. Study Design: Application of satellite imageries and GIS software for the production of updated topographic map of Anyigba Town in Nigeria. Place and Duration of Study: GIS Laboratory, Department of Geography and Planning, Kogi State University, Anyigba, Nigeria, between April and July 2012. Methodology: Satellite image processing, classification and vectorization, visually-aided interpretation, digitization and geocoding of features, using ArcGIS 9.2, ILWIS 3.3 Academia, AutoCAD 2010 and Microsoft Excel 2010 software. Results: Topographic map created through the integration of point map, contour line map, land use classification map, planimetric map, digital elevation model (DEM) and digital terrain model (DTM). The built-up area has grown in an omni-directional pattern, annexing most surrounding villages. It was discovered that Anyigba is characterized by a gentle undulating landscape architecture, with some areas of marked elevation and depression as against what was reflected in the old toposheets (248 NW and 268 SW) produced in 1973. The DEM and DTM generated from the 1973 toposheets and the satellite imageries of 2001, 2005 and 2008 showed that changes in the topography is a direct result of unplanned expansion of the built-up area. Conclusion: The method is considered relatively cheaper and time-effective for updating topographic maps in Developing Countries where resources are scarce. The study suggests periodic research to update the topographic map of Anyigba as part of contributions towards building the much required National Elevation Dataset (NED) and Geospatial Data Infrastructure (GDI) in Nigeria for updating environmental planning and management.