Problem with GIS Data

• Lots of different, related files

• Results in data that is:– Hard to find and share and of questionable

quality

• Need:– Containers for datasets:

• File Geodatabases?

– Standards for complex data: • Data Models?

– Protocols for maintaining quality: • ?

Data Complexity

• Shapefile:– shp: spatial data– dbf: attributes– shx: index– xml: metadata– prj: SRS

• Would be nice if this was all in one file

Sharing Tools

• Won’t it be great if we could use tools like model builder to work on the city of Arcata, then use the same tools to work on the city of Eureka, etc.

• Need a common format for all the spatial data– Roads, rail lines, parks, water mains,

parcels, hydrants, zoning areas, etc

Geodatabases

• Definition for a complex set of data

• Stored in a Geodatabase

• Easily shared

Data Model in a “Can”

ESRI Approach

• Create their own database structure within a database– Add user’s data into the Esri structure

• Personal File Geodatabase– MS-Access– Not supported in the future

• Relational Databases– Supported through Arc Spatial Database

Engine (ArcSDE)

• File Geodatabases

Arc Data Storage

Shapefiles Coverages GeoDatabases

Collection of datasets

Folder of Shapefiles

ArcInfo Workspace

GeoDatabase

Dataset Folder of Shapefiles

Coverage Feature dataset

Collection of features

Shapefile Feature class Feature class

Features Point, Multipoint, Polygon, Polyline

Point, Polygon, Polyline, etc.

Point, Multipoint, Polygon, Polyline, Network Annotation

File Geodatabase

• Advantages:– Easy to share complex vector datasets

• Disadvantages:– Internal structure is hidden– Basically, only supported by Esri products– Raster databases can be huge

• Note: – Geodatabases used to be the only way to fix

topology problems, now they can be fixed with shapefiles as well

File Geodatabase

• Folder with “.gdb” extension!

• Additional data types & capabilities:– Relationships– Topology Rules– Feature Dataset– Raster Catalog & Mosaic– Networks

• The default for data created from the tool box

New File Geodatabase

The “Can”

New Terminology

• Feature Dataset– Set of vector data (points, polylines,

polygons)– Common Spatial Reference

• Raster Dataset (not recommended)– Set of rasters– Common Spatial Reference

• Dataset is like a folder

• Name should include Spatial Reference– WGS84_UTM_10_North

New Feature Dataset

GDB with Feature Dataset

Feature Class

• Data for one layer of vector data

• Points, Polyline, or Polygon

• Has spatial data, attributes, metadata

• Effectively, a shapefile

New Feature Class

Feature Class vs. Shapefile

File Geodatabase Structure

• Disk– Folders…

• Geodatabase.mdb– FeatureSet

» FeatureClass» Relationships» Tables» Etc.

Data Color-codingyellow coverage

gray geodatabase

green shapefile

References• Arctur, D. and Zeiler, M., 2004, Designing

Geodatabases, ESRI Press• Lowe, J.W., 2003. Flexible data models strut the

runway. Geospatial Solutions, 13(2): 44-47.• Maidment, D.R., 2002. Arc Hydro: GIS for Water

Resources, ESRI Press, 203 pp. w/CD.• Li, X. and M.E. Hodgson, 2004. Vector-field data model

and operations. GISci. Rem. Sens., 41(1): 1-24.• Wright, D., Blongewicz, M., Halpin, P., and Breman, J.,

Arc Marine: GIS for a Blue Planet, Redlands: ESRI Press, 2007.

• In Digital Earth or dusk.geo.orst.edu/djl/arcgis/book.html