Research On IHO S-101 Electronic Chart Data Conversion Engine

Electronic chart system is a general term that uses computer technology,internet technology and other related technologies to display all kinds of digital nautical chart information on related application systems.At present,the international official electronic charts mainly use the S-57 series of international standards formulated by the International Hydrographic Organization.It mainly includes a series of standards such as IHO S-57 standard,IHO S-52 standard and IHO S-58 standard.S-57 standard is a transfer standard for digital hydrographic data,which released version 3.1 in 2000.For the development of electronic charts,the International Hydrographic Organization began to compile and develop a new geospatial standard for hydrographic data,freezing the main part of the S-57 standard.IHO released the S-100 Universal Hydrographic Data Model in 2010 and the S-101 Electronic Navigational Chart Product Specification based on this model in 2018.IHO is currently introducing S-1×× series product specifications,revising the S-65 Electronic Navigational Charts(ENCs)”Production,Maintenance and Distribution Guidance,and preparing to start the production of S-101 electronic chart data.IHO plans to use S-101 and S-57 standard electronic charts in parallel after 2024,and S-101 standard electronic charts will completely replace S-57 standard electronic charts after 2030.As a member of international maritime affairs and IHO,China does not have the ability to produce S-101 charts at present,so it is urgent to upgrade the electronic chart production system and provide users with the latest version of standard electronic charts.First of all,it is necessary to carry out preparatory work and complete the data conversion from S-57 standard electronic chart to S-101 standard electronic chart.In this paper,the electronic chart files of S-57 and S-101 international standards are taken as the research object,and the data model,data structure,file format,elements and attributes of S-57 and S-101 standards are compared and analyzed,and a data conversion system from S-57 chart to S-101 chart is developed in combination with S-101 Electronic Navigational Chart Product Specification and S-65 Electronic Navigational Charts(ENCs)”Production,Maintenance and Distribution Guidance.The system mainly includes three functional modules: S-57 standard electronic chart file reading and parsing module,data conversion module and S-101 standard electronic chart file packaging module.In the aspect of reading and parsing the S-57 standard electronic chart file,firstly,the data description record is parsed according to the ISO/IEC 8211 standard,and information such as record length,exchange level,version number,field length,field location and so on are obtained.Secondly,the file control field and data description field are parsed,and then the contents of five records in the electronic chart file,such as data set general information,data set geographical reference,points,edges and features,are sequentially parsed by using the field description information obtained by parsing the file control field and data description field to complete the reading and parsing of the S-57 standard electronic chart file.In the aspect of data conversion: according to the corresponding relationship between records and fields obtained by comparing and analyzing the data structures of S-57 standard and S-101 standard,the data structure of S-57 standard electronic chart file obtained by reading and analyzing is converted to obtain S-101 standard file records and fields,and at the same time,the sub-fields of elements and attributes in the fields are converted by using the XML document of element attribute conversion.In the aspect of S-101 standard electronic chart file packaging,firstly,the data description record is constructed,including the construction of data description record field area,the calculation of each field length and entry address information,the construction of record contents area,the calculation of record length and base address of field area and the construction of record header area.Secondly,nine kinds of records,including general information of data set,coordinate reference system of data set,information type,point,multipoint,curve,compound curve,curved surface and element type,are constructed in turn,including judging the data record type of electronic chart file,obtaining the names and quantities of record fields,constructing record field area,calculating the length and entry address information of each field,constructing record contents area,calculating the length and base address of record area and constructing record header area.So as to selectively open and read the S-57 standard electronic chart file and analyze it;Perform data structure conversion,element conversion and attribute conversion on the parsed data;According to the structure and content of S-101 standard file,read the data of electronic chart file in the system to construct chart file.Finally,this paper designs the prototype of IHO S-101 electronic chart data conversion engine by using Visual C++ MFC Microsoft Basic Class Library application based on the XML document of element attribute conversion,describes the development platform,workflow and functional modules of the system,and tests and analyzes the results of the system conversion case.The test results show that the research results have realized the data conversion function from S-57 chart to S-101 chart,and the conversion results basically meet the S-101 standard,which can be used in CARIS HPD series programs.It will provide basic support for the production of S-101 standard electronic chart in China.