West Africa Coastal Vulnerability Mapping: Subset of JRC Map of Accessibility

The West Africa Coastal Vulnerability Mapping: Subset of JRC Map of Accessibility data set is a 30 arc-second raster of travel time to major cities in West Africa within 200 kilometers of the coast. Extensive literature shows that road networks and market accessibility play an important role in development and access to health care and other social services. Greater spatial isolation is assumed to produce higher vulnerability to climate stressors. Market accessibility is defined as the travel time to a location of interest using land (road/off road) or water (navigable river, lake, and ocean) based travel. A team at the Joint Research Centre (JRC) in Ispra, Italy, created a global raster of accessibility using a cost-distance algorithm which computes the "cost" (in Units of time) of traveling between two locations on a regular raster grid. The raster grid cells contain values which represent the cost required to travel across them, hence this raster grid is often termed a friction-surface. The friction-surface contains information on the transport network, and environmental and political factors that affect travel times between locations. Transport networks can include road and rail networks, navigable rivers, and shipping lanes. The locations of interest are termed targets, and in the case of this data set, the targets are cities with a population of 50,000 or greater in the year 2000.

西非海岸脆弱性测绘：JRC可达性地图数据集的子集，为西非沿海200公里范围内至主要城市的旅行时间提供了一种30弧秒的栅格数据。大量文献表明，道路网络和市场可达性在发展、医疗保健及其他社会服务的获取中扮演着至关重要的角色。更大的空间隔离被认为会产生对气候压力因素的更高脆弱性。市场可达性被定义为利用陆地（公路/非公路）或水路（可航行河流、湖泊和海洋）旅行到达感兴趣地点所需的时间。意大利伊斯普拉的联合研究中心（JRC）的研究团队利用成本距离算法创建了一个全球可达性栅格，该算法计算了在常规栅格网格上两个位置之间旅行的“成本”（以时间单位计）。栅格网格的单元格包含代表穿越它们的旅行成本的价值，因此该栅格网格通常被称为摩擦面。摩擦面包含影响位置间旅行时间的交通网络、环境及政治因素信息。交通网络可以包括公路、铁路网络、可航行河流和航运通道。感兴趣的位置被称为目标，在本数据集中，目标为2000年人口超过5万的城市。