Spatial Data Management Platform (C # Development) based on arcgis10.0 and Oracle10g-Introduction to geographic information system (GIS)

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1. Geographic Information System (GIS)

GIS can be understood from three different perspectives. The first GIS is a spatial database, which contains a data model for expressing general GIS data (elements, grids, topologies, networks, and so on) the spatial database of the dataset. GIS Organizes spatial data into a series of topic layers and tables. Spatial datasets in GIS have geographical references, so they have location information in the real world and overlap with each other. In a GIS, geographic object sets of the same type are organized into layers, such as plots, wells, buildings, normal images, and raster-based digital elevation models (DEM ). A dataset consists of layers that interact with each other in a space.

Second, GIS is a map. GIS is a set of intelligent maps, and also a view for displaying the relationship between elements and elements on the surface. The underlying geographic information can be expressed in a variety of map modes, which can be constructed into a "Database window" to support query, analysis, and information editing. Spatial visualization refers to the form of map generation and other geographic information, including interactive maps, 3D scenes, presentations, charts, time-based views, and diagrams showing network relationships. GIS maps are similar to static and printed maps. what is different is that you can use them interactively. You can easily roam and scale an interactive map, so that some layers can be automatically displayed or closed at the appropriate scale. You can set symbols for a layer based on any attribute.

Third, GIS is a set of spatial data processing and analysis tools. From the perspective of spatial processing, GIS is a set of information conversion tools used to obtain new datasets from existing datasets. These spatial processing functions extract information from existing datasets, analyze the information, and finally import the results to the dataset. GIS is a series of operation tools for geographic datasets and applied to these datasets. Geographic data sets can be raw measurements (such as satellite images), Information parsed and compiled by analysts (such as roads, buildings, and land types ), you can also use analysis and model operations to obtain information from other data sources. Spatial Processing refers to the tools and processing processes used to generate derived datasets.

ArcGIS is a GIS product. In ESRI ArcGIS, arccatalog (GIS is a set of geographic data sets) and ArcMap (GIS is a smart map) are used separately) and arctoolbox (GIS is a set of spatial processing tools. These three parts constitute the key content of a complete GIS and are used at all levels in all GIS applications. ESRI's ArcGIS series software is a comprehensive, comprehensive, and scalable GIS software platform, you can use ArcGIS to build a geographic information system on the desktop, server, Internet, or in the wild.

ArcGIS Desktop is a complete suite of Professional GIS applications. ArcGIS Desktop is a software suite that integrates many advanced GIS applications. It contains a set of Windows desktop applications with user interface components (such as ArcMAP, arccatalog, arctoobox, arcscene, and arcglobe ). These tools can be used to design, share, manage, and publish geographic information. ArcGIS Desktop has three levels of products:

(1) ArcView (Basic edition): provides comprehensive plotting, data usage and analysis, and simple editing and data processing functions.

(2) arceditor (Advanced edition): provides all functions of ArcView, advanced editing, and editing of Shape files and Geodatabase.

(3) ArcInfo (Professional Edition): It is a full-featured table-level GIS flagship product. It provides more functions than arceditor to implement advanced geospatial data processing. It also contains the early command-based GIS product ArcInfo workstaion.

(4) ArcGIS Engine is an embedded development component used to develop GIS applications. With ArcGIS Engine, developers can ,. net and Java use simple interfaces to obtain a combination of any GIS functions to build a specialized GIS application solution. Developers can build a complete custom application through ArcGIS Engine or embed GIS logic into existing applications (such as Microsoft Word or Excel) to deploy custom GIS applications, distribution of GIS-oriented solutions for multiple users. ArcGIS Engine is a product for developers.

(5) server GIS includes ArcSDE, ArcIMS, and ArcGIS Server. ArcSDE is an advanced spatial data server that manages geographical information in multiple relational database management systems. ArcSDE is a data server located between other ArcGIS software products and relational databases, its wide application makes it possible to share a space database across multiple user groups across any network and scale up or down data of any size. ArcIMS is a scalable map server that publishes GIS maps, data, and metadata through the open Internet protocol. ArcIMS has been deployed in thousands of applications, mainly to provide data distribution and map services for Web users. ArcGIS Server is an Application server that contains a set of GIS software object libraries for building server GIS applications on enterprise and web frameworks. ArcGIS Server is a new product used to build centralized enterprise GIS applications, soap-based Web Services and Web applications.

(6) ArcPad is a solution for ArcGIS to implement Mobile GIS and Field Computing (such as recording and registering the spatial information of sudden accidents, these types of work can be done on a handheld computer device (running Microsoft Windows CE or Pocket PC) or tablet.

2. Spatial Data Representation

Spatial data is used to describe the targets from reality. Data is unified to indicate the shape, size, location, and distribution characteristics of spatial entities. Positioning means that the space target has a unique spatial location in a known coordinate system. Qualitative means the natural attributes of the space target, which are accompanied by the geographical location of the target; time refers to the change of the Space Target over time. The spatial relationship is usually expressed by the topological relationship. Spatial data is a kind of data that uses basic spatial data structures such as points, lines, surfaces, and entities to represent the natural world on which people depend. Spatial data is a special type of data. It refers to any data with spatial coordinates, such as architectural design drawings, mechanical design drawings, and various maps, expressed as numbers acceptable to computers.

There are many types of Spatial Data. Currently, common spatial data exchange formats include: ESRI's shape files and e00 formats; Autodesk's DXF and DWG formats; in addition, the National Space Data Association (NSDI) defines the unified spatial data conversion standard SDTS (spatial data transformation standard ), china's National Earth space data conversion standard and ogc gml.

There are so many spatial data formats, the conversion between them is also a key and difficult point of GIS-related technologies. Although many software provide space data format conversion tools, due to the complexity of geographical information, there is a lack of uniform description of spatial objects, the data models used to describe spatial objects in different data formats are different, which may lead to data loss during the conversion process. Therefore, the converted data cannot be accurate to the source data. In addition, this mode requires data unification, which violates the principles of data distribution and independence. Therefore, in the data format conversion mode, spatial data conversion standards and dynamic integration of network-oriented spatial data will be a hot topic in future research.

3. Metadata

Meta data is the data or information used to describe the data. These definitions are very abstract, and metadata can be simply understood as the smallest data unit. Metadata can describe its elements or attributes (name, size, data type, etc.) for data, or its structure (length, field, data column ), or its related data (where, how to contact, and owner ). For example, the personal information registration form we enter in our daily life, including name, gender, ethnicity, political outlook, one-inch photos, education qualifications, titles, and so on, is the metadata that locks a person.

Metadata can be divided into three types: Fixed metadata, management metadata, and descriptive metadata. Fixed metadata is the metadata related to the composition of things. Administrative metadata is metadata related to the way transactions are processed. Descriptive Metadata is the metadata related to the nature of things. Of course, it does not mean that all data can be clearly divided into the above three categories.

Metadata is of great significance to the information architecture. Metadata is a very effective method to ensure that all forms of content on the website can be found. For example, we often worry about searching for a beautiful image we saw a long time ago. If the information architecture of an image website is good enough, we can find it clearly with the metadata we recall. Metadata is like building bricks and tiles in the information architecture. It can be placed into different information retrieval systems as needed. Metadata is the basis of all organization systems. Navigation Systems from searching to e-commerce websites are strongly dependent on metadata. As mentioned above, metadata is actually a product's searchable service, and users do not search for information according to machine thinking, but directly enter descriptive information about the information, such: "Puppy Christmas card ". This means that when creating descriptive metadata, we should try to extract any stories about this object. These are the details that people can remember and get used to searching.

GIS also uses a lot of metadata [2], which is mainly used to describe spatial data, it describes the content, quality, representation, spatial reference, management, and other features of a geographical dataset in a structured manner. It not only provides search and navigation for spatial information data, but also facilitates data conversion, maintenance, understanding and use. It is the basis for achieving geospatial information sharing and is one of the important technical support conditions for the digital earth.

4. C #-based ArcObjects GIS Application Development

ArcObjects is ESRI (Environmental Systems Research Institute, Inc .) the company provides a GIS technical framework, which is a set of COM Component Object sets developed based on Microsoft's COM technology. This component set provides almost all of the underlying GIS functions, even ArcGIS software is developed using ArcObjects components. Because ESRI has developed the APIs of this component libraryProgramYou can also use ArcObjects to develop your own GIS applications.

The second GIS development using ArcObjects is to adopt a general software development platform such as C #. net, VB. net, VB, Visual C ++, Delphi, PowerBuilder, etc. ArcObjects function components are re-assembled according to the specific needs of the project, to integrate a more powerful and complex COM component or application. Using ArcObjects for component GIS secondary development [4] is currently the most popular, flexible, and stable GIS development method.

C # is the mother tongue of the. NET platform. Although. Net also supports various major languages that Java thinks, C # is obviously the first choice to develop. NET platform applications. In fact, many important applications of the. NET platform itself (such as ASP. NET) are written in C. Therefore, the development language of this system uses C #. net.