photograph: Desert Tortoise The Advanced Resource Technology Group:
The Knowledge Base



Last updated
6/19/02

ArcGIS Geodatabase: Information


Procedures | Knowledge Base | Back

Introduction

ArcGIS supports a new type of dataformat called the geodatabase. There are two kinds of geodatabases -- personal and multiuser. The personal geodatabase can only be edited by one person at a time and is stored in Microsoft Access format. The multiuser geodatabase can be edited by many users at the same time and is stored in Oracle, SQL Server, Informix, or IBM DB2. It also requies ArcSDE for editing. These geodatabases can be edited in ArcMap/ArcView, ArcEditor, or ArcInfo. The following table is a brief overview of the geodatabase capabilities for each module:

  ArcView/Map ArcEditor ArcInfo
Read, Display, Query, & Use Any geodatabase Any geodatabase Any geodatabase
Editing Edit simple personal geodatabases1

Can edit simple feature classes, annotation, tables, and simple feature datasets
Edit all geodatabases

Multiuser geodatabase editing requires ArcSDETM
Edit all geodatabases

Multiuser geodatabase editing requires ArcSDE
Schema management and database design Create simple schemas for personal geodatabases1

Supports: points, lines, polygons, annotation, and tables

No topology
No geometric networks
No relationship classes
No feature-linked annotation
No dimension classes
No raster support
No custom feature classes
Create all schemas for any geodatabase

Multiuser geodatabase support requires ArcSDE
Create all schemas for any geodatabase

Multiuser geodatabase support requires ArcSDE
1 Simple personal geodatabases model spatial features that are very much like ESRIŽ shapefiles: points, lines, and polygons without topology. Personal geodatabases also allow you to store multiple feature classes together in a single feature dataset, as well as provide annotation support.

The ART lab currently does not have any of the database software required to create a multiuser geodatabase, so these documents will focus on the personal geodatabase.





Personal Geodatabase

The personal geodatabase can include many types of data, including coverages, shapefiles, CAD drawings, INFO tables, and DBF tables. It does not support raster data. Because these datasets will be stored in the relational database Microsoft Access, they should be arranged into a logical database architecture (to be designed by you, the user). The personal geodatabase will be given a name of filename.mdb that is browsable and editable by the ArcGIS modules, but it can also be opened with Microsoft Access if you feel the need to see how Access is organizing your data behind the scenes. Figure 1 shows what the personal geodatabase can look like in ArcCatalog. ArcCatalog is the easiest and most straightforward way to create a personal geodatabase.

A screenshot of the personal geodatabase structure in ArcCatalog.

Fig. 1. A screenshot of the personal geodatabase structure in ArcCatalog.





Below is a zoom of the ArcCatalog tree view of the personal geodatabase, srer.mdb. The personal geodatabase can contain the following items:

Tree view of a personal geodatabase in ArcCatalog.



Feature Datasets

Feature Datasets

A feature dataset is equivalent to a directory or folder in a computer operating system. It is used to help organize the data into a logical structure. It can contain feature classes and relationship classes, but not tables.

The feature dataset, even though is is equivalent to a directory, must have a specified projection that is identical to the projections for the coverages/shapefiles to be stored inside of it. See the procedures section for instructions on how to define the coordinate system and import data.





Feature Classes

Feature Classes

The feature class is the coverage, shapefile, or CAD drawing. They can be stored at the root of the geodatabase or inside of a feature dataset. Remember that the personal geodatabase does not support raster data. You can create new feature classes or you can import coverages/tables/shapefiles as feature classes. You can also create relationships (called relationship classes, described below) between feature classes. See the procedures section for details.

Following is a description from the help documents under "How data is converted":

The feature class stores both the geometry and attributes from the input data. The feature class is automatically registered with the geodatabase system tables so that it can participate in relationships and geometric networks, have validation rules, and so on. Similarly, when a table is imported, a table is created in the geodatabase and automatically registered with the geodatabase system tables. Coverages, shapefiles, and CAD feature classes are imported into ESRIŽ simple feature classes. INFO and dBASE tables are imported into ESRI simple row tables.

Any table, shapefile, or coverage that is imported by some other mechanism will not be registered with the geodatabase system tables and therefore will not be a true geodatabase feature class or table. The ArcGIS system has tools to register these feature classes and tables with the geodatabase.





Tables

Tables

Tables can only be stored at the root of the geodatabase. You can store the following table formats: INFO, dBase, VPF, or OLE DB.

You can create relationships (called relationship classes, described below) between tables and feature classes.





Relationship Classes

Relationship Classes

The relationship class is identical to a relate in ArcInfo -- the two items to be related must have a common attribute (primary and foreign keys). The related information will show up in ArcMap if you do an Identify on a feature, and the related data can be edited through ArcMap, ArcInfo, or ArcEditor. To use the related information for symbology purposes in ArcMap, you must create a join in ArcMap, but you will be able to choose the relationship class on which to base the join instead of defining it again. You can read more about this in the procedures section.





Procedures | Knowledge Base | Back


The School of Renewable Natural Resources   The College of Agriculture & Life Sciences

CALS Privacy Statement