Introduction of GIS Application and OpenGIS

three major applications of GIS
The first category is the government application, "e-government" is the current government to strengthen the information construction of the new direction, refers to the modern computer, network communications and other technology support, government agencies day-to-day office, information collection and release, public management and other affairs in the digital, networked environment under the State Administration forms. GIS has become one of the necessary supporting systems in many government decision-making departments, and has played an important role in the National Water Conservancy, electric power, forest husbandry, geology, transportation, resources and environmental protection institutions.
The second type is enterprise application, with the arrival of Information age, enterprise organization, operation, management also gradually to the information direction development, GIS through provides the Visualization geospatial information Service unifies the Enterprise Management Information System, provides the auxiliary decision-making for the enterprise business planning, the logistics and so on.
The third category is the public application, the emergence of Webgis for the public to provide access to geospatial information Services platform, through the open, simple operation of Webgis services to meet the needs of the public geographical information, such as: convenient for people to travel Google, Baidu Map services.
three major components of GIS
(1) Digitized data
The digitized data is the representation form of information in the computer, it refers to the geo-spatial information that uses the computer hardware and software to carry on the graphical display and the spatial analysis operation. The data in GIS is different from other information system, it has the spatial characteristic, GIS data is divided into two categories: spatial data and non spatial data. For example, a GIS data longitude and latitude data indicates the space position of the thing, belongs to the spatial data, the name and the date data indicates that thing's attribute, belongs to the non spatial data, the GIS unifies the spatial data and the non spatial data to carry on the analysis, the processing.
GIS function
Basic functions should include: data entry, data editing, data storage, data manipulation, data analysis, data display and output
(1) Data input: Also known as collection
Artificial digital input remote sensing satellite image and GPS
(2) Data editing: With the digital operation of map elements, users need to complete all the space elements associated with their corresponding attribute data, clean up and correct the errors in the process of data conversion.
(3) Data storage: When data is digitized and edited, digitized map data needs to be stored on disk or other storage devices, and the most commonly used data models for storage are: Raster format and vector format. Both formats simplify the original image data into a common format that is easy to store.
(4) Data manipulation: When the data is stored in the system, the user can carry on a series of operations to the data, the GIS operation usually is provided to the user in the form of a tool bag, the toolkit includes basic data operation and analysis function, such as: Data retrieval, area perimeter measure, coordinate transformation, projection transform, picture edge and so on.
(5) Data analysis: GLS's core lies in its strong analytical ability, such as the search for various spatial elements within a certain range of an accident location, and the statistical analysis of the relevant information to provide the necessary information for the accident treatment. Remote sensing technology, Global positioning Technology and geographic information system are called "3S" technology
OpenGIS(Open Geodata interoperation specification,ogis--opened geo-Data interoperability specification)
Was proposed by the American OGC (OpenGIS Association, OpenGIS Consortium), the main architecture and class library

Geometry base Class library
Representative: JTS (Java), GEOS (c + +), shapely (Python)
This kind of geometric Foundation Class library mainly realizes the OpenGIS simple Feature access standard, simply says that they are to the geometric type (Geometry) to carry on the certain degree encapsulation. Taking JTS as an example, it implements the Java-based interface and inheritance relationship according to OpenGIS's description of geometry, and makes a class like point and linestring that can be used. In addition, these class libraries also generally realize the OpenGIS de-9im spatial position relation judgment and some commonly used computational geometry method (such as buffer) such software is the base of all GIS class libraries, just as geometry is one of the bases of GIS.

Data Source Implementation
Representative: PostGIS (PostgreSQL), MySQL Spatial
The realization of the data source is mainly the spatial expansion of the open source database. The spatial extension of a database does not only support geometric types of storage in a datasheet,

It also provides a SQL-level set-relationship judgment, such as a point in a polygon that can be directly exploited by SQL queries.

PostGIS is an open source project supported by Canadian Refractions Corporation, which provides space support for open source database PostgreSQL. After PostGIS installation, a template database appears in PostgreSQL, and when you create a new space database, you only need to PostGIS as a template. The PostGIS implements basic space operation functions at the SQL level. In addition, the vast majority of open source GIS software (even if not strictly adhere to the OpenGIS standard) support the PostGIS data table directly load, read and write functions. Undoubtedly, PostGIS is the best implementation of the OpenGIS data source.
The aim is to promote the adoption of new technical and commercial approaches to improve the interoperability of geo-information processing (interoperability),
It is dedicated to the elimination of geo-information applications (e.g., GIS, remote sensing, land information systems, automatic Mapping/Facility Management (AM/FM) systems)
and the barriers between geographic applications and other information technology applications, the establishment of a non "boundary", distributed, component-based geo-data interoperability environment

Middleware

Representative: Geotools (Java)
Middleware plays the role of connecting data and services in the system. Geotools undertakes the task of reading data from a variety of data sources, such as POSTGIS,GML,SHAPEFILE,WFS, and standardizing the data. The feature interface is defined in Geotools, and data from different data sources is read out and unified into the implementation of the feature interface that contains a geometry member (defined in JTS). In this way, the further operation can only be oriented to feature,
Eliminates the high-level software to the different data source interpretation process. In addition, Geotools is also a comprehensive implementation of the OpenGIS standard, including filter, coordinate conversion, GML.

Geotools and JTS also have geoapi what exactly is the relationship.
JTS is a set of open source Java APIs made by Vivid Solutions of Canada. It provides a set of core algorithms for spatial data manipulation. Provides a 2D spatial predicate API for basic geometric operations in a space object model compatible with the OGC standard.
Geoapi provides a set of Java interfaces for the OpenGIS specification.
Geotools is an open-source Java GIS Toolkit that can be used to develop standards-compliant geographic information systems.
Geotools provides an implementation of the OGC (Open Geospatial Consortium) specification as their development.
In simple terms: Geotools's goal is to develop a compliant GIS toolkit, and since it is a toolkit, there are a number of tools to deal with problems in building a complete geographic information system, common problems such as conversion of projections, setting of datum planes, rendering and styling of spatial data objects. , a variety of data source support, various GIS file format support, spatial data filtering and search .... And so on.
In the development of these tools, just in the processing of spatial data graphics relations, there is a very good solution, that is jts,jts solve the relationship between objects and objects to determine and calculate the topology, and provide a lot of useful algorithms to solve the object area, length ... And so on and so on. In this way, JTS is equivalent to a child module in Geotools. However, because the module itself is not Geotools engineering, so in Javadoc can not find JTS API, need to go to the JTS Web side of the other download. As for Geoapi, it is the Geotools standard template. It set out what all the data types in a geographic information system should be, and what kinds of specifications are in the way projections are converted. Such a compatible GEOAPI interface Geotools is a standard geographic Information System Toolkit.

WMS/WFS Server

The Web map Service (WMS) returns the corresponding map (including raster data such as PNG,GIF,JEPG or svg,web CGM vector data) According to the user's request.

Representative: GeoServer (Java), MapServer (PHP)
Map servers play the role of providing map services to clients in the network. This type of map server can receive a unified specification of WMS and WFS requests, returning data in a variety of formats. This process has the strict stipulation of the WMS/WFS specification, so, to the client what is the realization of its map server does not cause much impact.
GeoServer is OpenGIS WEB Server specification of the Community Open source project, using GeoServer can easily publish map data, allowing users to update, delete, insert the feature data, through the GeoServer It is easy to quickly share spatial geographic information between users.
GeoServer is compatible with WMS and WFS features, supports PostGIS, Shapefile, ArcSDE, Oracle, VPF, MySQL, MapInfo, supports hundreds of projections, and can output network maps as JPEG, GIF, PNG, SVG, KML format, can run on any j2ee/servlet container, embed Mapbuilder support AJAX map client openlayers;

Client
Representative: Openlayers/mapbuilder (JavaScript), Udig (Java), QGIS (c + +)
The client is divided into two types: browser and desktop client. The b/s system client represented by Openlayers is now very powerful, it can encapsulate WMS request, implement the slice load function of map in the browser. In addition, drag, zoom are also very perfect function, you can implement Cross-browser operation. The recent Openlayers version also supports the vector editing feature, which can be submitted via WFS-T. The traditional desktop client program features more powerful, supporting a variety of data sources including WMS and WFS, as well as editing function, operability is more powerful than the browser.

Data Format

ESRI's Shapefile format

Is the fact standard of the GIS vector file format, which is usually composed of. SHP,. Shx,. prj,. DBF and other documents. OpenGIS's implementation software generally supports Shapefile's reading and writing. Shapefile can be used directly as a data source in GeoServer, but this approach is not recommended, for the simple reason that file-based data sources can cause poor performance and data loss. The shape format file contains at least 3 files, and their suffixes are:. SHP, DBF,. Shx. shp stores Geographic shape and location information,. DBF stores property information,. SHX is an index file.

MapInfo. Mif/.mid format

. A MIF file that is used primarily to hold the geometric data of a space object; Mid file, which is mainly used to preserve the attribute data corresponding to the geometric data;

Gml

GML is one of the standard specifications for OpenGIS, which describes geographic data based on XML. XML is easier to read and write than to Shapefile, and is easy to propagate in various forms on the network. At the same time, XML is also readable, understandable and recognizable to people. Geotools implements Gmldatastore, so GML in GeoServer can also be used directly as a data source (a GML extension needs to be downloaded).
At the same time, GML data source provides the idea and possibility of realizing the data source dynamic.

Geographic Application Server

Mapinfo MapXtreme MapObject Autodesk
Map Guide
ArcIMS
Super Map

ArcGIS Server

The

Mapxtreme is a internet/intranet based application server developed by MapInfo, which has a powerful mapping function, including thematic maps, buffer analysis, map editing, map target lookup, map display, layer control, spatial selection, geo-coding, Expand the Map Library and sample data, and so on. As long as Administrators program and manage Mapxtreme on a Web server, users can access map information through a Web browser.
How it works
Mapxtreme how thin clients work in general, and the map that clients see is a picture of a format that the server dynamically generates based on user requests. Mapxtreme adopted is b/S mode three-tier architecture the client first submits the HTTP request to the Web server, submits the form form, and the Web server receives the request, submits the map operation request to the Map application service, The Map application service calls the Mapxserver in response to the user's operation request, carries on the corresponding spatial analysis and the processing, produces the new map picture, returns to the Web server, the Web server then embeds the picture in the HTML page and returns to the client's browser