WebGIS development practices manual 1.2.1-1.2.4

1.2.1. c/s GIS

The C/S-based network GIS is the most common distributed architecture. In this client/server architecture, geographic data is stored on the Geographic Data Server (such as large-scale relational databases such as ArcSDE), and data viewing and editing are implemented on the client. This architecture generally involves massive data, geographic computing, spatial analysis, thematic drafting, data conversion, and other factors. Therefore, it is only suitable for deployment in a stable LAN. At present, most of the geographic information management systems we can see use this model.

The C/S Mode GIS client is usually a desktop application built using some software development component sets.ProgramSuch as ArcGIS Engine. Of course, similar to ArcGIS desktop software and arcexplorer are also typical c/s client programs. These client programs have rich functions and good interfaces, but it is difficult to achieve rapid deployment and cross-platform deployment. At the same time, the client program requires high computer hardware performance.

In recent years, the C/s gis system has been weakened. On the one hand, it is caused by the difficulty of its development and deployment. On the other hand, this GIS system, which can only run inside and outside the local area, cannot connect to and process SDE, which makes our views increasingly pessimistic [1].

1.2.2. B/S GIS

B/S GIS is a distributed network GIS Based on Web browsers. It uses WWW as a programming environment and has inherent cross-platform deployment features, able to access a variety of GIS data and services in a heterogeneous Internet environment.

The B/S mode user interface is displayed in the browser. A small amount of transaction logic can also be implemented on the page through the script language, but the main transaction logic is completed on the server. This greatly reduces the client's Hardware requirements, reduces system maintenance and upgrade costs, but also puts forward high requirements on server performance. In the B/S mode GIS, it is very difficult to implement data editing Based on Web browser pages, which is one of the main reasons why we cannot implement rich functions like C/S. But generally, we can use technologies such as VML and SVG to draw simple images on the client.

B/idea); in some special applications, Vector Form WebGIS can also be implemented. There are many such methods, such as using the SVG plug-in the web browser to parse the GML data sent from the server, or, the data is directly transmitted to a self-developed GIS browser plug-in through the TCP protocol for resolution and display.

1.2.3. Mobile and Embedded GIS

Mobile and Embedded GIS are the products that combine GIS technology and embedded devices and are embedded system products with GIS functions. It is a hybrid system of hardware and software. It is mainly used for geographic data collection, query and positioning, and data management during the movement process.

The operating carrier of mobile and Embedded GIS is completely different from the PC we use. Its hardware is generally PDA, smart phone, or professional navigation equipment, and the operating systems are also different, such as Windows Mobile, Symbian, and Palm OS. Because mobile and Embedded GIS devices differ significantly from PCs in terms of performance, storage capacity, and other indicators, such GIS systems do not include advanced data analysis and processing capabilities, at the same time, it also puts forward higher requirements on the reliability of GIS software.

1.2.4. Web service-based GIS

GIS based on Web Services also transmits data through the HTTP protocol, which is a programmable logic for access using the HTTP protocol. The difference from the B/S mode GIS lies in the user's difference, the user of the former is a software program, while the latter is a person.

Web Service is a basic programming component provided in the Internet distributed computing environment. It provides distributed interoperability and cross-platform features. When using XML to transmit data, it can bypass firewall blocking. More importantly, it has open communication standards, such as data transmission standard soap and Service Description Language WSDL.

GIS based on Web Services uses these advantages of web services to publish geographic data. It also has a standard framework for geographic data discovery, access, representation, query, analysis, and integration, for example, the ows (OGC Web Services) framework proposed by OGC.

ESRI's ArcIMS, ArcGIS Server products, and open-source geoserver and other WebGIS servers support OGC-standard geographic services, and these services become more and more powerful. For example, in ArcGIS Server, not only does raster data and geoprocess scripts can be released through Web Services.

In addition, network-based GIS also has grid gis and other technologies, but so far it has only stayed in the theoretical and laboratory stages, and it is still time before the real use.

[1] ESRI seems to have seen this problem. Starting from arcgis9.2, its product focus has been gradually transferred to ArcGIS Server.