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- A geodb is an alternative way to store GIS information in one large file, which can contain multiple point, polygon or polyline layers.
- less messy compared to multiple shapefiles.
- often appear in single files .gdb or .mdb file extension
- in .gdb shape files are reffered to as "Feature Classes"
- geographic datasets of various types held in SQL, postgresql
- A key geodatabase concept is the dataset
3 Primary dataset types:
Feature classes - A table with a shape field containing point, line or polygon geometries fir geographic features.
Raster datasets - Contains rasters which represent continous geographic phenomena.
Tables - collection of rows, each containing the same fields. * Feature classes are tables with shape fields. *
GeoDatabase storage includes both schema and rule base for each geographic dataset + tabular storage of the spatial and attribute data.
The spatial representations in geographic datasets are stored as either vector features or as rasters. These geometries are stored and managed in attribute columns along with traditional tabular attribute fields.
A feature class is stored as a table.Each row represents one feature.
There are various implementation of the ESRI GeoDatabase information model and they can be categorized in two:
Single User GeoDatabases:
Personal GeoDatabase: Built on top of the ".mdb" MS Access format.
FileGDB: Built on top of a proprietary format created by ESRI (".gdb" folders)
Multi-user GeoDatabases (aka Enterprise GeoDatabases):
These are the datasources supported by the ArcSDE middleware.
'SDE defers spatial processing to the DBMS. If the underlying database system has no spatial support at all, SDE will implement all of the spatial functionality. If the underlying database has some functionality, SDE will implement some functionality and defer the rest to the database engine. To achieve the best performance and leverage core database technology, we try to defer as much functionality to the database as possible.