While this chapter has focused mainly on the ArcInfo coverage format, there are other types of vector formats that you can use in ERDAS IMAGINE. The primary types are:
- GeoMedia Warehouse
- Spatial Database Engine (SDE)
Shapefile Vector Format
The shapefile vector format was designed by Esri. You can use shapefile format (extension .shp) in ERDAS IMAGINE. You can:
- display shapefiles
- create shapefiles
- edit shapefiles
- attribute shapefiles
- symbolize shapefiles
- print shapefiles
The shapefile contains spatial data, such as boundary information.
You display GeoMedia feature geometries and attribute data in the IMAGINE Workspace through connections to warehouses where the data is stored. Each warehouse connection uses a data server to convert the data into a format that the software can display. Connections are links that allow the transfer and translation of feature data from the various supported data warehouse types.
To create or open a GeoMedia Warehouse, you must first establish a warehouse connection. A warehouse is a database that contains features and their geometry.
The New Connection dialog establishes and modifies the connection to GeoMedia database warehouses. You specify the name and location of the connection and all the necessary connection parameters.
Like the shapefile format, the Spatial Database Engine (SDE) is a vector format designed by Esri. The data layers are stored in a relational database management system (RDBMS) such as Oracle, or SQL Server. Some of the features of SDE include:
- storage of large, untiled spatial layers for fast retrieval
- powerful and flexible query capabilities using the SQL where clause
- operation in a client-server environment
- multiuser access to the data
ERDAS IMAGINE has the capability to act as a client to access SDE vector layers stored in a database. To do this, it uses wizard dialogs to connect ERDAS IMAGINE to a SDE database, and selects one of the vector layers. Additionally, it can join business tables with the vector layer, and generate a subset of features by imposing attribute constraints (for example, SQL where clause).
The definition of the vector layer as extracted from a SDE database is stored in a <layername>.sdv file, and can be loaded as a regular ERDAS IMAGINE data file. ERDAS IMAGINE supports the SDE projection systems. Currently, ERDAS IMAGINE’s SDE capability is read-only. For example, features can be queried and AOIs can be created, but not edited.
SDTS stands for Spatial Data Transfer Standard. SDTS is used to transfer spatial data between computer systems. Such data includes attribute, georeferencing, data quality report, data dictionary, and supporting metadata.
According to the USGS, the implementation of SDTS is of significant interest to users and producers of digital spatial data because of the potential for increased access to and sharing of spatial data, the reduction of information loss in data exchange, the elimination of the duplication of data acquisition, and the increase in the quality and integrity of spatial data (United States Geological Survey, 1999c).
The components of SDTS are broken down into six parts. The first three parts are related, but independent, and are concerned with the transfer of spatial data. The last three parts provide definitions for rules and formats for applying SDTS to the exchange of data. The parts of SDTS are as follows:
- Part 1—Logical Specifications
- Part 2—Spatial Features
- Part 3—ISO 8211 Encoding
- Part 4—Topological Vector Profile
- Part 5—Raster Profile
- Part 6—Point Profile
ArcGIS Integration is the method you use to access the data in a geodatabase. The term geodatabase is the short form of geographic database. The geodatabase is hosted inside of a regional database management system that provides services for managing geographic data. The services include validation rules, relationships, and topological associations. ERDAS IMAGINE has always supported Esri data formats such as coverages and shapefiles, and now, using ArcGIS Vector Integration, ERDAS IMAGINE can also access CAD and VPF data on the internet.
There are two types of geodatabases: personal and enterprise. The personal geodatabases are for use by an individual or small group, and the enterprise geodatabases are for use by large groups. Industrial strength host systems such as Oracle support the organizational structure of enterprise geodatabases. The organization of both personal and enterprise geodatabases starts with a workspace that contains both spatial and non-spatial datasets such as feature classes, raster datasets, and tables. An example of a feature dataset would be U.S. Agriculture. Within the datasets are feature classes. An example of a feature class would be U.S. Hydrology. Within every feature class are particular features like wells and lakes. Each feature class will be symbolized by only one type of geometry such as points symbolizing wells or polygons symbolizing lakes.
It is important to remember when you delete a personal database connection, the entire database is deleted from disk. When you delete a database connection on an enterprise database, only the connection is broken, and nothing in the geodatabase is deleted.