Research On Collaborative Mapping Key Technology Based On Map Edit Long Transaction Model

Collaborative mapping is an effective way to improve the efficiency of cartography,rapid updating map products and geospatial database.At present,there are relatively more collaborative researches on purery text,image editing and graphic design in the field of CSCW,while there are relatively few researches on collaborative editing design of maps(including a large number of graphics,images,text,OLE,etc.).There are relatively more common relational transactions researchs based on DBMS or DFS,while there are relatively fewer spatial data editing transactions involve complex relationships.In collaborative mapping,there are relatively more researches on interactive editing of maps by foreground users,while there are relatively few researches on permanent synchronous writing the foreground editing data to background geographic information database.Research on the map editor long transaction model oriented to collaborative mapping,solving the key technical problems in collaborative mapping are significantly important to keep data consistency of map data at the front desk and the background of geographic information,to improve the multi-user collaborative mapping UI coordination and synchronization,and to balance cartography and geoinformation production enfficiency and its quality.Aiming at several key problems existing in collaborative mapping,such as not high editing transaction execution and processing efficiency,complex map editor long transaction concurrent processing,and difficulties in coordination and synchronization of multiple clients' map diaplay,the key technologies of collaborative mapping based on Map Editing Long Transaction(MELT)model are studied and practiced.The main contents are as follows:1.The research background and current situation of collaborative mapping are analyzed.The shortcomings of current research are pointed out.The key technologies of collaborative mapping based on MELT model are proposed,and the research scope and basic ideas are clarified.2.The theries and methods of collaborative mapping,the concepts of MELT are introduced.After analyzing the research status at home and abroad,it summarized several key technical problems existing in collaborative mapping.It also summarized the core issues of long-term transaction of traditional GIS and the research difficulties.3.The MELT model is designed by simulating collaborative mapping MET(Map Editing Transaction)to map document status and its change.The methods of how to manage and manipulate the status and change data of map document based on virtual memory and common memory are proposed respectively.The principle of Map Document Agent MET is explained,and the MET list management is designed.The detailed structure of the map document model is designed.Extended modeling of OLE for a special mapping object is carried out to support transaction operation simulation of OLE object.4.The technology of organizing and scheduling collaborative mapping transactions based on single and double lists are studied.The serial protocol of collaborative mapping MET is designed.The method of dealing with intersecting and concurrent transactions is proposed.The connotation of automatic transaction and user-long transaction in collaborative mapping is expounded.The automatic method of Graphics Relation Considering Processing(GRCP)is studied and designed.A multi-client synchronous display technology for collaborative mapping based on vector grid hybrid pyramid index is presented.5.A centralized collaborative mapping experimental platform,CoMapping system,is constructed.A software module for multi-source data integration of map documents based on MELT was developed.A functional framework for map element editing was constructed.Several typical GRCP map editing problems were solved experimentally.On this basis,using map data of different scales and data sizes,the transaction management capability is test.Transaction concurrency processing experiment and multi-client map synchronization cooperative display experiment based on map document simulation are carried out.Wether the MELT model suitable for collaborative mapping mechanism and wether the solution effect to the key technologies of collaborative mapping are verified.At the end of this paper,the following innovations are summarized:(1)Dynamic single backup based on virtual memory and static multi-backup based on disk and memory improved the traditional MELT model.Through state backup of map documents and change data storage management,the database MET was successfully simulated,which overcomes the long time transaction execution problem and DDL operation shortcomings.It improves the efficiency of MET execution and the management ability of MET.(2)A triple model of collaborative mapping transaction is designed.Several concurrent processing rules of MELT are established.The concurrent processing methods based on optimization,merging and discarding of collaborative mapping MELT are realized.The serialization of collaborative mapping transaction is supported.The ACID characteristics of MELTs are maintained,and the consistency of map editing results data is ensured.(3)Designed and implemented data model and processing method for typical cases,such as the processing of double-line road intersections,the automatic processing of map graphics overlapped by annotations which have the same color.These processing did not affect other map editing processes.It was not only significantly reduced the amount of editing transactions and user editing workload,but also significantly reduced the amount of map document state change data size after each MELT.(4)A vector-raster mixed pyramid index is designed.A test platform CoMapping is improved from Drawpile.A map synchronization display mechanism is established,which significantly improves the synchronization and coordination of collaborative mapping view display.