Data Structures & GeoDatabase

Data Structures & GeoDatabase GeoDatabase

NEW! • In 9.2 the GDBs have significantly changed • Mostly for the better • New names (file, personal, scaleable) • Easier to move data between GDBs • Do NOT have to specify the EXTENT of the GDB – a big problem in 9.1 and earlier.

The Geodatabase It is a single container for many feature classes (FC) (layers, {themes} of any feature class type) Quite often the FCs are stored in Feature Datasets (FDS) Shapes become Feature Classes (FC) Data in a FDS can be topologically linked

GeoDatabase Now • Three flavors of GDB • File • Personal • Scalable (was called Enterprise) • Supports a model of topologically integrated feature classes - 2D & 3D • Supports Data Models -- ArcHydro • Use can be simple or very complex! • In some applications database designers will be needed to tune the database operation! • Can use many different data structures

The possibilities… From ESRI’s course Learning ArcGIS Desktop

GeoDatabase • Three flavors of GDB • File • Personal • Scalable (was called Enterprise)

File GDB • Stored as folders in a file system. • Can scale up to 1 TB in size. • This option is the currently recommended GDB • Only one user can edit at a time • Is much faster than other flavors

Personal GDB • Stored within a Microsoft Access data file, which is limited in size to 2 GB. • One editor at a time

Scaleable GDB • Also called an ArcSDE Geodatabases • Stored in a relational database using Oracle, Microsoft SQL Server, IBM DB2, or IBM Informix. • These multi-user Geodatabases require the use of ArcSDE and can be unlimited in size and numbers of users. • Much more complex and require professional computer types

Scaleable GDB • Also called an ArcSDE Geodatabases • Stored in a relational database using Oracle, Microsoft SQL Server, IBM DB2, or IBM Informix. • These multi-user Geodatabases require the use of ArcSDE and can be unlimited in size and numbers of users. • Much more complex and require professional computer types ArcSDE = Spatial Database Engine

How do they look • In ArcCatalog • In Windows Explorer

Catalog View WE view Views of GDB

WE view Catalog View Views of GDB

Advantages of GDBs • Can be moved as one piece of data regardless of how much stuff is in it or where it is! • Faster (particularly for File GDBs) • Can use between layer topology for FC in a FDS • Can actually get into the Personal GBD Access database and mess with it (but you had better know what you are doing!)

Advantages of GDBs • TOPOLOGY? = the arrangement that defines how point, line, and polygon features share coincident geometry. • examples, • Fire hydrants must fall on water mains, • Adjacent soil polygons must share their common boundaries. • Can be moved as one piece of data regardless of how much stuff is in it or where it is! • Faster (particularly for File GDBs) • Can use between layer topology for FC in a FDS • Can actually get into the Personal GBD Access database and mess with it (but you had better know what you are doing!)

Feature Classes Stand alone Feature Classes Geodatabase Feature Dataset Source View

} Cover Line(arc) poly Anno Table point ArcCatalog view Display view

} Cover These are in a FDS and thus valves can be snapped (must be actually) to pipes ArcCatalog view Display view

More yet: Feature Class (FC) • Conceptual representation of a category of geographic features. • Includes point, line, poly & annotation • When shapefiles are added to a GDB their computer representation is changed • This is why you cannot drag and drop a shapefile into a GDB. • You have to load it or Import it.

Feature Dataset (FDS) • A collection of feature classes that share the same spatial reference. • It is because they share the same spatial reference that they can participate in topological relationships with each other. • Several feature classes with the same geometry may be stored in the same feature dataset. • Object geometry and relationship classes can also be stored in a feature dataset

There are new icons in a GDB

Icons GDB Feature Dataset GDB table

Annotation

Vector data: Network

Table Field Properties • When creating a Feature Class or table you can specify the number of fields to be included • And you can spec settings such as field type and max. size • All fields have property default values, domains, aliases, and null allowance

Topologies • Many datasets have features that could share boundaries or corners • By creating a Topology you set up rules defining how features share their geometries. • Editing a boundary or vertex shared by two or more features updates the shape of all of them.

Topology rules • Govern the relationships between between features within a FC or features in different FCs • Example: moving a slope boundary in in one FC could update two slope class polys AND update a forest stand boundary in another FC. • Topology editing tools in ArcMap are used to create and change the rules

Geometric Networks • Some vector datasets need to support connectivity tracing and network connectivity rules • Communications • Pipelines • Transportation (roads, railroads, canals) • Geometric networks allow you to turn simple point and line features into networkedge and junction features

Summary of data types

Creating a GDB • In ArcCatalog! • Point to where you want to put the new GDB • Click New>Personal GDB • Type in a new name

Adding data • In Catalog… Right click and select New • You get

Copying data • You can copy/paste data between GDBs • OR • You can import shapefiles, coverages, computer-aided drafting (CAD) data, and GeoDatabase FCs into a GDB

Importing shapefiles • feature class that's in another coordinate system. • You MUST project to the spatial definition of the GDB • Then right click on GDB and select Import --------- 

Planning • What is the problem? • What data is needed (scale, extent, etc.0? • What kinds of relationships are needed between FC? • How will the data be organized (FDS)?

SUMMARY • The new GDB structure is much improved • Easier to use • 3 kinds • Drop and drag between GDBs • Extent does not have to be defined before creating

Data Structures & GeoDatabase