Research On K Nearest Neighbors Query In Road Network In Forestry Location Based Service Platform

The forestry information construction is an important guarantee to the transformation of "digital forestry" to "smart forestry". To better serve the forestry,it is an urgent need to combine mature, advanced technology with innovative ideas. Location Based Services refers to a mobile information service based on spatial location that has merged the wireless positioning, GIS, Internet, wireless communications, databases, and other related technologies. It is a based technology to provide users with including path guide, location query, emergency command, emergency call, and many other services by getting the locations of the mobile user information. The technology is widely used in the emergency rescue, personal locator, vehicle navigation, staff scheduling and so on. Therefore, it has good development prospects. The Location-based services technology servers for forestry,which has an important supporting role to promote the construction of forestry information and accelerate the development process of the "wisdom forestry".According to the urgent need of intelligent management in personnel management and emergency command in the forestry sector, this paper analyzes the key technology to build forestry location services platform, and makes an in-depth study on the issue of the k nearest neighbors query of the moving objects in road network in location based services as well as constructs the forestry location service monitoring platform, which provide support for personnel locating, route planning and command dispatching in personnel management and emergency command.The main research work and innovative points are the following aspects:Expounding the key technology in location based service,and analyzing the question to need to be resolved in all key technology steps..According to the characteristics of the forest environment, the research method and research means are proposed.Road network model is the foundation of the K nearest neighbors query in road network.Combining the analysis of the advantages and disadvantages of the road network model which have already existed with the characteristics of forest road network,We put forward a road network model based on the route model,which can represent the rule of one-way road,two-way road and the turn rule in crossroad.The moving objects and road network are not independent existence for the moving objects index in the road network. So the moving objects and road network should be indexed simultaneously in index structure. The static road network and the dynamic moving objects should be stored respectively from the perspective of query performance and update performance of index structure. Based on the idea,the paper comes up with the three-tier index structure,which indexing the static road network with R tree, indexing the moving objects with hash table and indexing the road edge connection relationship with adjacency list.The problem of K-nearest neighbor queries in road network is rerearched based on the established road network model and the moving objects index structure. In order to meet the fast response of query request in location based services platform, one hand,the shortest path between the road edge node should be calculated by using precomputation technology.on the other hand, considering that the direction relationship is always took into account as a query constraints, the direction relations constraints is introduced into the nearest neighbor query problem. So the K nearest neighbor query algorithm based on the direction relationship constraint is raised to improve query speed of algorithm. Experimental analysis results show that the PC_KNN algorithm based on precomputation technology and CDR_CKNN algorithm based on direction relation constraint have excellent query performance.Relying on " the monitoring technology based on the Internet of Things and the applied research projects in forestry", Based on the existed GPS interphone in forestry department, the wireless sensor devices built by the project and Research ideas of location services technology,using WebGIS technology,GPS positioning technology, wireless communication technology and spatial database technology,the forestry location services platform is builded to realize the display,query,browsing etc. basic operation based on forest geographic information and the application of location based service,which includes the personnel location data acquisition, position monitoring, track playback, dispatching etc..By researching the key technology of Location Based Service platform in forestry construction, the paper can solve the following problems,including the position,monitoring and tracking of forest rangers, fire vehicles and forest fire point, data storage and management, information query and map display,Which provides scientific, accurate, efficient solution for daily management. Through the study of K nearest neighbor query problem in the road network, it can improve the query request of Location-Based Service and provide scientific and effective guidance for implementation of personnel management and making fire decision. Therefore, the research plays the role of enriching the content of forestry informatization construction and accelerating the process of forestry informationization.