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321.
The Alburni massif (1742m a.s.l.) stretches NW–SE, about 23km long and 9–10km wide, covering 246km2 with an average elevation of about 940m a.s.l. This massif, with more than 500 caves, is the most important karst area in southern Italy. The karst channel network is hierarchically organized: some channels feed a major spring (1m3/s) with a very short transit time while others communicate directly with the basal water table related to other springs (Q > 3m3/s).There are several dolines and swallow holes just above the basal water table and in the urbanized areas; for years a swallow hole directly transferred pollutants into the aquifer. The contamination vulnerability map shows that the prevalent vulnerability degree ranges from high to very high, due to the widespread karstification of the area and to the presence, on the plateau, of large vegetated areas with gentle slopes favouring fast infiltration.Hence it is important to ascertain the human impact on the area and the consequent contamination risk of the aquifer of the Alburni karst area. Three main layers were created to assess groundwater contamination risk: the vulnerability map, the hazard map, and the value map.The groundwater contamination risk map stresses the importance in a park area of aquifer vulnerability, which strongly influences the risk: indeed, the prevalent moderate degree of risk in the final map depends on the high vulnerability and the low hazard degree. However, in the future it is crucial to take into account the nature of the agricultural land use allowed in the park, which could increase the hazard degree and consequently the risk degree. 相似文献
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地图符号识别是地图成图自动化的一个重要研究方向,但是传统的地图符号识别方法已经不能满足数字地图发展的需要,迫切需要一种用自动化技术代替人工数字化的作业方式[1].因此地图符号的识别是整个技术的关键,而点状地图符号的识别更是地图符号识别的基础.本文探讨和研究了基于神经网络的点状地图符号识别. 相似文献
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PASCO公司以提供地理信息为基轴的新信息服务,产品用于专业网站的网上地图查询,面向电脑及手机的地图服务及结合GPS技术的车载导航系统等,同时与信息技术紧密结合充分运用于地图的数字化处理、数据分析、信息提取和自动维护、信息发布等诸多方面。 相似文献
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Can Yang Győző Gidófalvi 《International journal of geographical information science》2018,32(3):547-570
Wide deployment of global positioning system (GPS) sensors has generated a large amount of data with numerous applications in transportation research. Due to the observation error, a map matching (MM) process is commonly performed to infer a path on a road network from a noisy GPS trajectory. The increasing data volume calls for the design of efficient and scalable MM algorithms. This article presents fast map matching (FMM), an algorithm integrating hidden Markov model with precomputation, and provides an open-source implementation. An upper bounded origin-destination table is precomputed to store all pairs of shortest paths within a certain length in the road network. As a benefit, repeated routing queries known as the bottleneck of MM are replaced with hash table search. Additionally, several degenerate cases and a problem of reverse movement are identified and addressed in FMM. Experiments on a large collection of real-world taxi trip trajectories demonstrate that FMM has achieved a considerable single-processor MM speed of 25,000–45,000 points/second varying with the output mode. Investigation on the running time of different steps in FMM reveals that after precomputation is employed, the new bottleneck is located in candidate search, and more specifically, the projection of a GPS point to the polyline of a road edge. Reverse movement in the result is also effectively reduced by applying a penalty. 相似文献
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针对我国当前交通拥堵现状并结合城市具体交通状况,本文提出了以天地图为基础的交通引导系统设计方案。通过对交通信息的搜集、分析,制作专题信息地图,在引入Ajax引擎工作模式的基础上,将交通道路信息分析成果以地图形式进行网络发布,反映交通道路的拥堵程度。驾驶员通过移动端浏览器可以直观地掌握所处时段的交通状况,系统通过时间依赖方法可以为驾驶人员寻找出行耗时少的最优驾驶路线,从而避免由于驾驶员对交通信息掌握不明导致的车辆集中,缓解城市道路交通压力,减少交通拥堵现象。 相似文献
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探讨了线状地图符号的特点,从视觉变量出发针对线状地图符号的设计方法进行了理论研究,提出了线状符号多样化设计的思想。之后以应急专题地图符号为例,进行了应急专题地图线状符号的多样化设计,并通过眼动实验进行了验证。 相似文献