The Research Of Map Update Technology Of Change Spans For Land-Use Change Survey On Mobile Devices

Changes of land types, property boundaries administrative division etc are investigated by field survey, Incremental data package and statistical table are produced and reported, Land-use database is updated. Aiming at the incorrect indoor update because of field data omit or error, map update technology of change spans on mobile devices is researched in this paper. It is used to ensure the validity of changes by the preliminary identification of field collecting data.Key technologies of map update technology are researched, such as polygon clipping algorithm, D-9 intersection model calculation method and map update technology of change spot are designed and implemented. To improve the efficiency of polygon clipping algorithm, the palne sweep method is used to compute intersections, and a single-linked list is used as data structure. The method is proposed to solve the repeated point or repeated edge, which discrimates between the entry intersection and the exit intersection by line direction relations. The test results show that the improved algorithm could clip result polygon accurately and efficiency. Spatial geometric objects are decomposed by the data structure of plannar graph, the local topology information of elements in the plannar grah is calculated and the value of 9-intersection model is updated, so the topological relation between spatial geometry objects is identified. The geometric update operations of change spots are designed. The geometric difference of map update methods is implemented by directed-edges, and its’ feasibility testing is completed. With topological relations between spatial geometric objects, which are used to the decision of map update regions and operations, the technical process of map update is designed. The inspection of land types and the merge operation of error land types are implemented. The test has done. At last, the map update software of change span based on Android is designed and implemented, and the software works well.It is used in the field change investigation, the map update of change spans in different change types is implemented,60 change spans are updated in 3 second, and the map update method is stable running in mobile devices, the workload is reduced.