Remote Sensing and Digital Databases to Recovery Terrestrial Boundaries in West Africa – Cape Roxo Region

Abstract

This case study focuses on borderlands located in Guinea Bissau, more specifically on the borderland of Cape Roxo region, with a controversial geographic location which have been raising great interest and several disputes, mainly due to the lack of geographical information. This study intends to contribute to clarify the problem combining geographical information and multitemporal analysis to define the exact position of some boundary beacons. The geographical information used, includes all available data, from old and actual maps and technical reports to most recent data obtained from new geospatial technologies. Historic and geographic information, describing the Guinea Bissau boundaries, combined with ancient aerial photographs (1950-1960) and recent high spatial resolution satellite images (2013), WorldView-2, are used in a Geographic Information System (GIS) to perform the multitemporal study. The spatial resolution of WorldView-2 images was improved using several pan-sharpening algorithms to combine multispectral and panchromatic bands in order to obtain a pansharpened image with higher spatial resolution. This procedure enhances the spatial information improving the interpretation of terrain features. Multitemporal analysis detected changes in coastal landforms, in Cape Roxo region, showing significant shoreline erosion/accretion, a high dynamic lagoon-beach system and relative stability of the inshore dune, where a boundary beacon is located.