[Abstract]
This paper expounds the advantages of developing digital mapping system with GIS as the core based on component GIS, as well as the design goal of digital mapping system with GIS as the core and the coding scheme of basic terrain elements. Combined with the development process of SuperMap Survey, this paper also introduces how to design and implement a professional digital mapping system based on GIS kernel.
In order to solve the data conversion problem between digital mapping system and geographic information system, it is necessary to develop a digital mapping system dedicated to geographic information system. This paper discusses the advantages of developing GIS management system based on COM GIS technology. In addition, the goal of GIS DMS is listed, and how to code GIS entities is explained. In particular, SuperMap Survey is used to discuss the details of developing DMS for GIS.
[Keywords:]
Digital mapping system takes GIS as the core and SuperMap Survey as the design goal of component GIS.
Digital mapping system for GIS, component GIS, target, hypergraph measurement
1. Introduction
Digital mapping technology is one of the most commonly used mapping technologies at present, and the electronic data provided by digital mapping system is also a very important data source of GIS. The seamless connection between electronic data provided by digital mapping system and GIS data is also one of the difficult problems to be solved urgently in the development of GIS. Although there are many digital mapping systems in the domestic and foreign markets at present, they have not solved the existing problems well so far. After the electronic data submitted by digital mapping system enters GIS, the main problems are:
(1) There is widespread information loss during data conversion. Because most traditional digital drawing systems are developed based on CAD kernel, they focus on the description of spatial geometric information; However, geographic information system requires the joint storage and management of spatial information and attribute information, which leads to the loss of not only spatial information but also attribute information during data conversion.
(2) After data transfer, it often cannot meet the requirements of GIS directly, and a lot of post-editing work is needed, which not only wastes resources, but also prolongs the construction cycle of the system.
(3) It is difficult to maintain and update the basic database of GIS. Because of the frequent data conversion in the process of maintenance and updating of GIS and digital mapping system, it is often impossible to directly operate the basic database, which makes it inconvenient to maintain and update the basic data.
(4) In the process of data conversion, in addition to information loss, it is often accompanied by data expansion. The result of data expansion sometimes leads GIS to be unable to manage these "massive" data.
There are many reasons for the above problems. To sum up, there are mainly the following reasons:
(1) Complexity and diversity of data. It is mainly manifested in the complexity and diversity of the real world, and the inconsistency in the description and expression of the same spatial object in different mapping systems.
(2) Different understanding of GIS. Developers of different digital mapping systems have different understandings of GIS and lack of corresponding unified standards as reference, which leads to differences in data expression.
(3) Due to the limitation of basic development platform and development power, digital mapping systems often cannot take into account the data requirements of GIS. At present, most developers of digital mapping system are not the developers of GIS basic platform, which also affects the communication between digital mapping system and GIS more or less.
At present, there are many digital mapping systems in the market, which can be divided into two types according to the development mode: (1) CAD system as the secondary development platform. These systems make good use of the flexible editing and powerful drawing functions of CAD system, but because of the huge difference in data structure between CAD system and GIS, their data often can not meet the requirements of GIS. (2) Digital mapping system based on independent platform. Although such a system does not have to stick to the restrictions of secondary development, it has great flexibility in development. However, the development of such a system needs to start from the bottom completely, which is difficult, long-term and costly. The emergence of ComGIS technology provides a new development method and idea for developing digital mapping system with GIS as the core.
2. Component GIS technology and its advantages as a development platform for digital mapping system.
2. 1 what is component GIS technology?
Component-based software technology has become one of the development trends of software technology. Component-based development (CBD) is a revolution in software development. Different from new trends such as object-oriented and client/server, component-based development is not only a new distributed computing model, but also a broad architecture that supports the concept of life cycle computing including design, development and deployment.
Because component-based development is highly reusable and interoperable, it will affect all aspects of application portfolio, including all types of clients, application servers and database servers, and will have a far-reaching impact on all aspects of application development.
Two important specifications of component-based development are Microsoft COM/DCOM and OMG CORBA. At present, Microsoft's COM/DCOM occupies a leading position in the market, has been widely used, and has gradually become the de facto standard in the industry. Based on COM/DCOM, Microsoft introduced ActiveX technology, and ActiveX control is the most widely used standard component in today's visual programming.
The so-called component GIS refers to GIS based on component object platform, which is provided by a group of components with certain standard communication interfaces and allowing cross-language applications. This kind of component is called GIS component, and the interaction between GIS components and between GIS components and other components can be realized through standard communication interfaces, and this interaction can even be realized across computers.
At present, GIS manufacturers at home and abroad are very optimistic about the development prospect of component GIS platform, and have launched their own GIS products. For example, SuperMap2000, a full-component GIS platform launched by Beijing SuperMap Geographic Information Technology Co., Ltd., MapEngineer developed by Beijing Tuyuan Company, MapObjects of ESRI, MapX of MapInfo, etc. Fortunately, the domestic component GIS platform can compete with foreign similar products in function, even better than foreign similar products in many aspects, which makes the development of digital mapping system with GIS as the core have more choices.
2.2 Advantages of developing digital mapping system by using component GIS
The emergence of component GIS provides a new development method for developing digital mapping system with GIS as the core. Compared with the traditional development method, its advantages are as follows:
(1) Component GIS itself is a complete GIS, and its data model is completely consistent with GIS. Based on this, the development can ensure the good compatibility between digital mapping system and GIS.
(2) Component GIS has flexible development means. We can freely choose our familiar computer languages for development (such as VB, VC, Delphi, C Builder, etc.). ) without having to learn the secondary development language. Component GIS provides two different development levels, one is based on ActiveX controls; The second is the direct development of the bottom class library (SDK) based on component GIS. We can choose flexibly according to our own needs.
(3) Component GIS completely encapsulates the functions of GIS, so that developers can concentrate on the realization of professional functions, which greatly reduces the development difficulty and development cycle.
(4) The digital mapping system based on component GIS has good scalability. Component GIS can be seamlessly integrated with other systems, including digital mapping systems, and developers can directly use the written program code; Component GIS platform is often composed of multiple components, and developers can choose new components to upgrade the system at any time according to the needs of the system. With the enhanced functions of the component platform, developers can directly use the enhanced underlying functions without recompiling the whole program, which greatly reduces the difficulty of system maintenance and upgrade.
Table 1 Comparison between development means using ComGIS and traditional development means
The development method is based on ComGIS platform and CAD platform, and is completely developed by the bottom.
Poor compatibility with GIS.
Is it difficult to take GIS as the core?
Support for spatial databases is mixed.
The development difficulty is low and the development difficulty is high.
The development cycle is short and long.
The investment in development is very small.
Good scalability is generally better.
There are many options for developing languages.
Do you support visual development?
Whether the copyright is independent is yes, no, yes.
Design of Digital Cartography System Based on GIS
3. 1 system design objectives
After years of development, the traditional digital mapping system has formed a relatively complete theoretical and technical system. However, the rapid development and wide application of GIS technology put forward higher requirements for digital mapping system. The emergence of component GIS technology provides an ideal development means for the transformation from traditional digital mapping system to digital mapping system with GIS as the core. Compared with the traditional digital mapping system, the digital mapping system with GIS as the core needs to achieve the following goals in design:
(1) takes GIS as the core and faces GIS. This requires that the data requirements of GIS should be fully considered in the process of system development, so as to solve the problems existing in the current mapping system data entering GIS. Taking GIS as the core is the soul and essence of the whole system design.
(2) Give consideration to the dual needs of cartography and GIS. While meeting the needs of GIS, we should also consider the requirements of cartography for data expression, the core of which is the symbolic expression of entities.
(3) Open design. The data requirements of different regions and different GIS are very different, which requires the digital mapping system to have greater flexibility and customization to cope with the ever-changing changes. The content of customization should include entity code, entity attribute, entity hierarchy and so on.
(4) Support spatial database. In recent years, spatial database technology based on large relational databases (such as Oracle, SQL Sever, etc.). ) has been widely used in GIS engineering construction. How to store, manage, maintain and update data directly on the basis of spatial database is one of the urgent problems to be solved.
(5) Multi-source data integration. At present, there are many electronic data formats and GIS data formats of digital mapping system. If the digital mapping system has good support for these data formats, it will greatly reduce the difficulty of data storage and solve the data bottleneck problem in GIS engineering construction.
(6) The operation is simple and conforms to the working habits of operators. The workload of GIS-oriented digital mapping system will inevitably increase. The digital mapping system with GIS as the core must provide efficient and simple operation methods to improve work efficiency.
(7) standardization and standardization.
3.2 Basic Terrain Data Coding Design
Terrain data coding is a key word that uniquely identifies elements in g is. The design of basic terrain data coding is also the need of mapping in g is, and it is also the basis of realizing the enjoyment of basic spatial information. The coding of basic topographic data is the basis of developing digital mapping system with GIS as the core, and it is also one of the keys to the success of the system. When designing the basic terrain data coding, we must follow several principles: (1) conforms to the national and industrial standards. (2) Convenient application. According to different needs, users can extract basic terrain information according to layers and thematic elements, and customize thematic display and output at will. (3) The system is easy to realize. In the actual design, it can be extended on the basis of the national basic terrain element coding to meet the actual needs of the system.
In the development of the actual system, we adopted the classification and coding scheme of urban basic geographic information based on entity characteristics. The feature of this scheme is that on the basis of the classification of geographical elements, the classification and characteristic attributes of entities that constitute geographical elements are added, which can better meet the application requirements of GIS mapping and analysis. For the details of this coding, please refer to the article "Urban Basic Geographic Information Classification Coding Scheme Based on Entity Features" (Liang Jun, Jin Wenhua), which is not repeated here.
The following is a coding example of terrain features.
Code = terrain feature classification code (4 digits) terrain feature code.
Such as: 1 1 1 0 2 0 (coding of triangle point symbols)
3.3 Functional design of the system
In the functional design, the digital mapping system with GIS as the core must take into account the dual needs of surveying and mapping and GIS. According to its workflow, it can be divided into the following modules:
(1) data input module In this module, several commonly used data acquisition methods should be supported. Including: field digital mapping (surveying and mapping), scanning vectorization, electronic data in other formats (GIS data and CAD data). In the data input module, it is also necessary to support spatial database as its data source.
(2) Editing module. This is the core module of digital mapping system with GIS as the core. In the editing module, the creation process of all GIS entities must be completely encapsulated by the system and completed automatically.
(3) Query, statistics and analysis. Based on the existing system, some common and simple query, statistics and analysis functions can be directly completed.
(4) Output module. Including several aspects: drawing output, report output, GIS data output in other formats, and direct storage of data in spatial database.
4. Implementation of SuperMap Survey, a digital mapping system based on GIS.
4. 1 component GIS platform selection
Supermap survey is a digital mapping system completely based on GIS developed by Beijing Supermap Geographic Information Technology Co., Ltd. In the choice of component GIS platform, we choose-SuperMap2000 as the development platform of SuperMap Survey. SuperMap2000 is a full-component GIS platform launched by Beijing SuperMap Geographic Information Technology Co., Ltd. Compared with other ComGIS platforms, SuperMap2000 is more suitable as the basic platform for the development of digital mapping system with GIS as the core, mainly because:
U SuperMap provides two levels of development means: ActiveX control and SDK. In particular, it provides the development means of SDK, which is especially suitable for developing such a system.
U multi-component composition. SuperMap2000 is composed of SuperMap core control, SuperWorkspace, SuperLegend, SuperTopo, Super3D, SuperLayout and other components, which has great flexibility in the selection of components and greatly enhances the expansibility of the whole system.
U open line type and symbol making function. SuperMap 2000 has built-in powerful line editor and symbol editor, allowing users to design new lines and symbols according to professional needs.
Powerful drawing, editing and capturing functions. SuperMap2000 provides editing and capturing functions comparable to CAD, which narrows the gap between GIS and CAD systems in this respect.
U Unique seamless integration technology of multi-source spatial data (SIMS). SuperMap 2000' s data conversion function can conveniently enjoy the geographic data of other GIS software platforms and provide the ability to convert various data formats.
U spatial database support. The spatial database engine of Hypergraph can directly support the storage and management of spatial data based on large relational databases (such as Oracle and SQL Server). ).
4.2 SuperMap survey implementation
When developing SuperMap Survey, we adopted the underlying SDK of SuperMap, and the programming language was Visual C 6.0 With the support of SuperMap SDK, we expanded our functions to meet the needs of digital mapping system. In the data storage structure, we adopt the SDB format data storage structure provided by SuperMap2000. Its biggest advantage is that it adopts double file structure instead of the common storage method of one layer and one group of files, which is conducive to maintaining the integrity of data. In the aspect of editing drawing, we further expand the editing function provided by SuperMap and add the editing function suitable for digital drawing. The system supports other formats of spatial database and GIS data based on SuperMap2000 spatial database technology and SIMS technology.
After intense development, based on the SDK of SuperMap2000, we have initially completed the development of digital mapping system with GIS as the core, and basically achieved the design goal of the system. In the hypergraph survey, we have realized the following functions:
(1) Common surveying and mapping methods supporting field digital mapping. Including measurement and recording methods (including electronic notebook) and comprehensive data acquisition (electronic tablet). SuperMap Survey can be used for conventional large-scale digital mapping.
(2) Vectorization of scanned images. SuperMap Survey supports image import, registration, cropping, registration and screen vectorization of common image formats.
(3) Support spatial database operation based on SQL Server and Oracle. You can edit the data in the database directly.
(4) Support the import and export of GIS data and CAD data in various formats.
(5) It is suitable for editing and capturing functions of digital mapping system. Fully automatic GIS entity creation. Cadastral survey module customized for cadastral survey.
(6) Provide the most commonly used GIS query, statistics and analysis functions.
(7) Standard map output based on template.
(8) Open design. Using the parameter management program provided by SuperMap Survey, various parameters can be customized conveniently.
Figure 1 Digital mapping system based on SuperMap2000 and GIS as the core.
Five conclusions
The development of digital mapping system with GIS as the core has solved the problem that electronic data provided by traditional digital mapping system enter GIS, and achieved good results in practical application.
In the process of system development, we deeply realize that ComGIS, as the development platform of digital mapping system, has moderate development difficulty, short development cycle, small development investment and good compatibility with GIS, and is an ideal choice for developing digital mapping system with GIS as the core.
[References]
[1] Chen et al., Geographical introduction to information systems, Science Press, Beijing, 2008+0.
[2] Yang Delin et al., Principles, methods and applications of large-scale digital mapping, Tsinghua University Publishing House, Beijing, 1998.2.
[3] Song, Zhong Ershun, "Research and Development of Component Geographic Information System", Journal of Images and Graphics, Vol.3, No.4, 1998.4.
[4] Geographic Information Industry Development Center of China Academy of Sciences, Coding and Layering Scheme of Basic Topographic Information of Hangzhou Land Information System, February 2000.
[5] Beijing SuperMap Geographic Information Technology Co., Ltd., Understanding SuperMap GIS, 2000.9.
I don't know how to send pictures.
Please check the resources yourself.