Multi-scale display of point data sets at the client side

IEEE GRSS; The Geographical Society of China<span class="MedBlackText">Multi-scale representation of geographic features is one of the research focuses of Geographic Information System (GIS). Most of the work has been done at the server side, especially when dealing with massive lines and polygons data by using spatial database technology. This paper discusses the issue about multi-scale display of point data sets, and presents a solution which is implemented at the client side. This solution overcomes the problem of losing some points of interest and their attribute. It also promotes the efficiency of displaying large point dataset with limited pixels. First, we process the level of details at the client side to avoid communicating with the server side at every scale but only at the first process. This strategy greatly decreases the time consumption in querying the server and network transmission. Second, when doing multi-scale manipulations at the server side (including spatial database), some points at certain scales will lose; some points more or less at certain scales will be disposed. However, by processing at the client side, because it contains all of the point data sets, this problem is solved. At last, this paper designs an adaptive algorithm to resolve the contradiction between small screen area and large point data sets with the tedious overlap phenomenon in displaying. A case study verifies the optimized display effect and improved efficiency of the proposed approach.</span

An effective algorithm for spatial query using spatial adaptive grid index filter

IEEE Geoscience and Remote Sensing Society (IEEE GRSS); East China Norm. Univ., Sch. Resour. Environ. Sci.; Shanghai Urban Dev. Inf. Res. Cent.; The Geographical Society of Shanghai; East China Univ. Sci. Technol., Bus. Sch.<span class="MedBlackText">Spatial query is the core function of GIS analysis, the query data is mostly geometric point, line, polygon which has the location information and formatted query condition is a variety of spatial relationships. We focus on the spatial query efficiency improvement with the query data in case of large and complex, and propos an effective spatial adaptive grid index filter algorithm for spatial query. It is different from the commonly used uniform grid index algorithm as it constructs the adaptive grid index of data using the spatial distribution information then it can radically improve the efficiency of spatial query. This algorithm contains four steps, including boundary grid index construction, internal grid index construction, primary spatial query and advanced spatial query. It is realized by C++ language and verified by experiments, the spatial query efficiency than the traditional uniform grid index algorithm has significantly increased.</span

Design of dynamic load-balancing algorithm of WebGIS farm

This paper analyzes the characteristic of state-of-the-art WebGIS system, proposes a model based on cluster technology for improving system performance. The algorithm, named adaptive map-based request distribution(AMBRD), is used as the core component of load-balancer considering the factor of general loads index feed back from GIS server nodes. A test-bed is established to verify the algorithm's practicality

an effective algorithm for spatial query using spatial adaptive grid index filter

Spatial query is the core function of GIS analysis, the query data is mostly geometric point, line, polygon which has the location information and formatted query condition is a variety of spatial relationships. We focus on the spatial query efficiency improvement with the query data in case of large and complex, and propos an effective spatial adaptive grid index filter algorithm for spatial query. It is different from the commonly used uniform grid index algorithm as it constructs the adaptive grid index of data using the spatial distribution information then it can radically improve the efficiency of spatial query. This algorithm contains four steps, including boundary grid index construction, internal grid index construction, primary spatial query and advanced spatial query. It is realized by C++ language and verified by experiments, the spatial query efficiency than the traditional uniform grid index algorithm has significantly increased. &copy; 2011 IEEE.IEEE Geoscience and Remote Sensing Society (IEEE GRSS); East China Norm. Univ., Sch. Resour. Environ. Sci.; Shanghai Urban Dev. Inf. Res. Cent.; The Geographical Society of Shanghai; East China Univ. Sci. Technol., Bus. Sch.Spatial query is the core function of GIS analysis, the query data is mostly geometric point, line, polygon which has the location information and formatted query condition is a variety of spatial relationships. We focus on the spatial query efficiency improvement with the query data in case of large and complex, and propos an effective spatial adaptive grid index filter algorithm for spatial query. It is different from the commonly used uniform grid index algorithm as it constructs the adaptive grid index of data using the spatial distribution information then it can radically improve the efficiency of spatial query. This algorithm contains four steps, including boundary grid index construction, internal grid index construction, primary spatial query and advanced spatial query. It is realized by C++ language and verified by experiments, the spatial query efficiency than the traditional uniform grid index algorithm has significantly increased. &copy; 2011 IEEE

A Novel Dynamic Physical Storage Model for Vehicle Navigation Maps

The physical storage model is one of the key technologies for vehicle navigation maps used in a navigation system. However, the performance of most traditional storage models is limited in dynamic navigation due to the static storage format they use. In this paper, we proposed a new physical storage model, China Navigation Data Format (CNDF), which helped access and update the navigation data. The CNDF model used the reach-based hierarchy method to build a road hierarchal network, which enhanced the efficiency of data compression. It also adopted the Linear Link Coding method, in which the start position was combined with the end position as the identification code for multi-level links, and each link traced up-level links consistently without recording the array of identifications. The navigation map of East China (including Beijing, Tianjin, Shandong, Hebei, and Jiangsu) at 1:10,000, generated using the CNDF model, and the real time traffic information in Beijing were combined to test the performance of a navigation system using an embedded navigation device. Results showed that it cost less than 1 second each time to refresh the navigation map, and the accuracy of the hierarchal shortest-path algorithm was 99.9%. Our work implied that the CNDF model is efficient in vehicle navigation applications

VGIS-COLLIDE: an effective collision detection algorithm for multiple objects in virtual geographic information system

National High Technology Research and Development Program of China (863 Programme) [2009AA12Z331