2011

Properties
Each feature class has properties that define it. The Pole feature class would
have properties such as identification number, name, model, material, height,
installation date, and so on. The properties that define a feature class can have
data types, default values, and constraints. These can help ensure that a feature
meets certain criteria in order to be included in a particular feature class. For
example, the “Large Roads” feature class can include a field called “Lanes.”
The constraint for “Lanes” can specify that its value must be six or higher in
order for a road to be included in the “Large Roads” feature class.
Data stores
Features can be stored in a spatial database (such as Oracle, MySQL,
PostgreSQL/PostGIS, or SQLServer), or in the ESRI ArcSDE data store, which
can use either an Oracle- or SQL Server-based spatial database. Features can
be stored in a file (such as SQLite, SHP, or SDF). Related SHP files might be
stored in a folder.
Features can be accessed from a web-based service (such as WFS or WMS).
AutoCAD Map 3D also supports ODBC (Open Database Connectivity), a
standardized interface for accessing a database from a program.
A data store usually contains a spatial context, which describes the spatial
metadata or parameters within which geometry for a collection of features
resides. The spatial context can specify the coordinate system, extents, and
tolerance. A data store can include multiple spatial contexts, for example, one
context for ground-based data and another context for schematic data.
For more information about features, feature classes, and schemas (including
diagrams that illustrate these concepts), see “What Are Features?” and “What
is a Schema?” in Best Practices for Managing Geospatial Data, available from the
Help menu in AutoCAD Map 3D.
Working with features in your map
To add a feature to your map, you connect to its data store and select the
feature classes to include. After you connect to a data store in AutoCAD Map
3D, that data store is a
feature source (page 2063) for the current map. Feature
sources are listed by provider (for example, all SDF feature sources are listed
together in Data Connect). Each feature class you add becomes a feature layer
(page 2063) in your map. You can apply filters and spatial queries to the layers
to show only some of the features within that layer. Filters are based on
attributes, and queries are based on spatial location.
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