Research On Cross-media Electronic Document Expression Method Supporting Spatial Data Research On Cross-media Electronic Document Expression Method Supporting Spatial Data

With the wide application of geographic information,the research on the combination of GIS and electronic documents has received more and more attention.As an important way of information transmission,electronic documents have the characteristics of ease of use,portability,readability,etc.However,traditional electronic documents embed spatial data into electronic documents in static manners such as picture and text description space information,and there is no real store spatial data inside the document.Therefore,this paper proposes a cross-media electronic document expression method that supports spatial data,in view of the insufficient expression of spatial data in electronic documents.This method extends the traditional structure of electronic documents,adds spatial data as a new type of information to its structure by directly compiling encoding files,and studies and designs the expression balance algorithm of spatial data in electronic documents with the help of generalization,which can better solve the limitations of usability,portability and readability of traditional electronic maps,and make it easier to distribute,save and share spatial data.Because PDF documents as the mainstream way of electronic documents have cross-platform and cross-media characteristics,this paper takes PDF as an example,and establishes a cross-media visual display platform for geographic information results through practice,which realizes convenient location service based on electronic documents and verifies the feasibility of this method.The main research contents of this paper are summarized as follows:1)A cross-media electronic document supporting spatial data(MapPDF)concept is proposed.Traditional electronic documents only describe spatial data in a static way and do not provide any GIS-related functionality.In response to this problem,this paper adds spatial data as a new information type to the traditional electronic document structure,and uses PDF to have high compression ratio,small data volume,easy to transfer and store,and PDF is used as an example to propose a cross-media electronic document expression method supporting spatial data.2)Design of data representation equalization algorithm for cross-media electronic documents supporting spatial data.In order to solve the load balancing problem of spatial data in electronic document in multi-scale expression process,this paper designs the MapPDF data expression equalization algorithm in the preprocessing and data representation of spatial data visualization.Taking the residential area elements as an example,the optimal information entropy is taken as the constraint condition,and the factors such as topological consistency,rank priority and measurement rationality are considered comprehensively.The topological rules,semantic rules and measurement rules of element selection are defined,and the algorithm design of MapPDF data expression equilibrium is completed.3)Design of data organization method for cross-media electronic documents supporting spatial data.Aiming at the problem that PDF can only represent static spatial data at a single scale,the traditional organization structure of electronic documents is expanded.The spatial data type is added to the organization structure of PDF information by directly writingencoding files.A map information package is designed based on GeoPackage specification,which realizes the multi-scale representation of spatial data in electronic documents.4)Based on the MapPDF designed in this paper,the cross-media visualization platform of geographic information results is researched and developed.Using the platform to create MapPDF files and provide weak GIS functions such as map dynamic browsing,hyperlinks,coordinate positioning,measurement,retrieval,etc.,realize the dynamic expression of spatial data in electronic media,print media and network media,and the feasibility of the cross-media electronic document expression method supporting spatial data designed in this paper is verified.