How to differentiate shapefile, coverage, and Geodatabase

How to differentiate shapefile, coverage, and Geodatabase (reprinted) in the past 20 years, vector data models have seen the greatest changes in GIS. For example, each new software package developed by ESRI corresponds to a new vector data model. ARC/INFO corresponds to coverage, ArcView corresponds to shapefile, and ArcGIS corresponds to Geodatabase. Coverage and shapefile are geographic relational data models. They use separate systems to store spatial data and attribute data, while geodatabase is based on object data models, it stores space data and attribute data in a unique system. Coverage is topological, and shapefile is non-topological. Coverage supports three basic Topological Relationships: connectivity, surface definition, and joining. The shapefile polygon actually has duplicate arc segments for the shared boundary and can overlap with each other. Unlike the multiple files used by coverage, it stores two basic files in the geometric nature. SHP is the geometric feature of file storage elements with the extension. spatial indexes of geometric features of elements retained by files with shx extension. Shapefile: A file format that stores GIS data based on files. It should be made up of at least. SHP,. DBF, And. shx files, respectively, storage space, and the relationship between attributes and the former two. Is a common data format in GIS.
Coverage: A topological data structure. Its principles are discussed in general GIS principles. The data structure is complex. properties are stored in the info table by default. Currently, ArcGIS still has some analysis operations that can only be performed based on this data format.
Geodatabase: a data format launched when ArcInfo was developed to ArcGIS. It is a data format stored Based on RDBMS, which has two categories: 1. personal geodatabse is used to store small amounts of data in the MDB format of access. 2. ArcSDE geodatabse stores large data in large databases such as Oracle, SQL Server, and DB2. Concurrent operations can be implemented, but independent user permission is required. Coverage data model
Coverage is a set that can contain one or more element classes. Before the first commercial GIS software ARC/INFO, the graphic representation of the computing Plan originated from the common CAD software. The attribute information and geometric elements are put together, which is not conducive to the description and analysis of spatial information.
Advantages of coverage:
(1) spatial data is associated with attribute data. Spatial data is stored in binary files with indexes. attribute data is stored in DBMS tables, and the two are associated with public identifiers.
(2) the topological relationship between Vector Data is saved.
Shapefile Data Model
The shapefile is ArcView GIS 3. the native data format of X is a simple element class. It uses the shape of point, line, and polygon to store elements, but cannot store topological relationships. It has the advantages of simple and fast display. A shapefile is composed of several files. The spatial information and attribute information are stored separately. Therefore, it is called "file-based ". Each shapefile consists of at least three files. *. SHP stores the spatial information of geometric elements, that is, XY coordinates. *. Shx stores *. SHP stores the index information, which is recorded in *. in SHP, how is space data stored, where is the input point of XY coordinates, and how many XY coordinate equivalence information are there. *. DBF is a DBASE table that stores the attribute information of geographic data. These three files are basic files of a shapefile. The shapefile can have other files, but all these files have the same name as the shapefile and are stored in the same path. The following briefly introduces some other common files :*. prj if shapefile defines a coordinate system, its spatial reference information will be stored in *. in the prj file ;*. SHP. XML: the XML Metadata File generated after metadata browsing on the shapefile ;*. SBN and *. sbx stores the spatial indexes of shapefile, which can accelerate the reading of spatial data. These two files are generated after data is operated, browsed, or connected, you can also use arctoolbox> datamanagement
Tools> indexes> Add spatial index tool.
Several common shapefile files: arccatalog automatically maintains data integrity when creating, moving, deleting, or renaming a shapefile using arccatalog, or using ArcMAP to edit a shapefile, synchronize and change all files. Therefore, you need to use arccatalog to manage shapefile. Although shapefile cannot store topological relationships, it is not a common graphic file used for display. As geographic data, it has its own topology. For example, for a polygon element class, shapefile sorts all its vertices in clockwise direction, and then edge vectors connected to each other in vertex order, inside the Polygon on the right of the vector, the left side of the vector is the exterior of the polygon. The rapid development of geographic information and ArcView in the 1990 s
GIS 3.x is widely used in shapefile format and has many data sources. Many software products provide interfaces for shapefile conversion (such as Mapinfo and MAPGIS ). ArcGIS supports editing shapefile and converting shapefile to the third-generation data model Geodatabase.
Geodatabase data model
Geodatabase, as the native data format of ArcGIS, reflects the advantages of many third-generation geographic data models. With the development of IT technology, the management mode of common transactional data has already changed from traditional file-based management to the management of relational databases based on industrial standards, the advantages of this database-based management method are self-evident. Can geographic data with spatial information be managed using this very mature database technology? ESRI introduced the Geodatabase data model, which uses the database technology to efficiently and securely manage our geographic data.
Geodatabase can be divided into two types: Microsoft Access-based personal Geodatabase, and Oracle, SQL Server, Informix, or DB2-based enterprise Geodatabase, because it requires middleware ArcSDE to connect, nterprise geodatabase is also called ArcSDE Geodatabase. Due to the limitation of Microsoft Access capacity, the size of personal geodatabase is limited to 2 GB, which obviously cannot meet the storage requirements of enterprise-level massive geographic data. Therefore, Geodatabase can be extended to ArcSDE.
Geodatabase, the underlying database can use a large relational database such as Oracle to store almost "infinite" massive data (limited by the size of the hard disk ). Although the underlying databases are different, Geodatabase provides users with a consistent operating environment. In Geodatabase, it not only stores simple element classes similar to shapefile, but also stores element sets similar to coverage and supports a series of behavior rules to verify the spatial information and attribute information, such as tables, association classes, grids, and notes. and dimensions can be used as eodatabase object storage. In perasonal Geodatabase and ArcSDE
Geodatabase is the same (grid storage is slightly different, but it is the same for users ).
GeoDatabase Model Structure:
(1) object class)
An object class is a special class with no spatial features. Its instance is a table record that can be associated with a specific behavior. For example, the owner of a plot can establish a certain relationship between the plots and masters.
(2) feature class)
A feature class is a collection of similar spatial elements. Such as rivers, roads, vegetation, and cables. Element classes can exist independently or have some connection. When different element classes have relationships, they are organized into a feature dataset.
(3) feature Dataset)
A feature dataset consists of a group of feature classes with the same spatial reference. Reasons for putting different element classes into the element Dataset:
A. Topic classification indicates that different element classes belong to the same category. For example, for water system data of a certain scale nationwide, the element types of the dot and line surface can be organized into the same element dataset.
B. Create a ry network-various element classes that act as the connection points and edges in the same ry network and must be organized into the same element dataset. For example, there are various switches, transformers, and cables in the distribution network, which correspond to the elements of the point or line type respectively. During the modeling of the distribution network, we need to take all of them into account the corresponding geometric network model of the distribution network. These element classes should be placed under the unified element dataset.
C. Consider a plane topology-a feature class that shares common geometric features. For example, land, water system, administrative region, etc. When moving one element, the public part also needs to move together, and the public ry remains unchanged.
(4) relationship class)
Define associations between different element classes or object classes. For example, we can define the relationship between the house and the owner, and between the house and the plot.
(5) geometric Network
A new class established on the basis of several element classes. When defining a ry network, we specify which element classes are added to it and what roles it plays in the ry network. For example, to define a water supply network, we specify the element classes corresponding to the "valves", "Pumping Stations", and "connectors" of the same element dataset to join and play the "connection" role; at the same time, we need to specify the "Water Supply Manager", "Water Supply Branch", and "Household Management" that belong to the same element dataset to join the water supply network, it plays the "edge" role.
(6) domains
Defines the valid range of an attribute, Which is continuous or discrete. (7) validation rules that constrain the behavior and values of element classes. For example, pipe connections of different pipe diameters must pass through suitable joints, and one or three owners can be owned in a land block.
(8) raster Datasets
Used to store raster data. Supports massive raster data and image mosaic. You can create a pyramid index to specify a visible range to improve search and display efficiency.
(9) tin Datasets
The typical data model of ARC/INFO, which uses the sample values of irregular distribution to form an irregular triangle set. Used to express terrain or other types of spatial continuous distribution features.
(10) locators
A combination of Positioning Reference and positioning methods. Different positioning methods are used for different references. For Positioning Reference, different positioning information has different expressions. In Geodatabase, there are four types of positioning information: Address encoding, <X, Y>, Place Name, zip code, and path positioning. The Positioning Reference Data is placed in the database table, and the locator generates a Spatial Positioning point on the map based on the positioning reference data.