1. Intro. To GIS Lecture 4 Data: data storage, creation & editing

2. How is data stored? Shapefiles are still a popular format
Consist of several separate files:
.dbf = attribute table
.prj = projection file
.shp = contains geometry information
Geodatabases are becoming more common
File vs. Personal Geodatabase

3. Geodatabase
The geodatabase is the common data storage and management framework for ArcGIS. It combines "geo" (spatial data) with "database" (data repository) to create a central data repository for spatial data storage and management. It can be leveraged in desktop, server, or mobile environments and allows you to store GIS data in a central location for easy access and management.

4. Geodatabase The geodatabase offers you the ability to:
Store a rich collection of spatial data in a centralized location.
Apply sophisticated rules and relationships to the data.
Define advanced geospatial relational models (e.g., topologies, networks).
Maintain integrity of spatial data with a consistent, accurate database.
Work within a multiuser access and editing environment.
Integrate spatial data with other IT databases.
Easily scale your storage solution.
Support custom features and behavior.

5. Kinds of Geodatabase
The geodatabase is a "container" used to hold a collection of datasets. There are three types:
File geodatabases — Stored as folders in a file system. Each dataset is held as a file that can scale up to 1 TB in size. The file geodatabase is recommended over personal geodatabases.
Personal geodatabases — All datasets are stored within a Microsoft Access data file, which is limited in size to 2 GB.
ArcSDE geodatabases — Also known as multiuser geodatabases. Stored in a relational database using Oracle, Microsoft SQL Server, IBM DB2, IBM Informix, or PostgreSQL. These geodatabases require the use of ArcSDE and can be unlimited in size and numbers of users.

6. Where does data come from?
Many sources for existing geospatial datasets (we’ve been discussing this and will continue to do so)
Field data collection
GPS
Surveys
Photo interpretation
Orthophotos
Satellite imagery
Vector: Initially, somebody had to digitize all the points, lines, and polygons
Raster: Data often a product of remote sensing

7. The “old-fashioned” way…
Paper maps digitized using a digitizing tablet
Handheld “puck” used to pinpoint locations and trace features

8. “Heads-up” digitizing
Also known as on-screen digitizing
Scanned digital format maps or aerial photographs used to create data:
trace features and record locations
Paper maps require a large format scanner
Images must be georeferenced once in GIS
Can still be very time-consuming

9. USGS Topographic Maps

10. MrSID

11. Creating new features Create New Shapefile Point, polyline, polygon
Coordinate System
Empty attribute table

12. Creating new features Before you start to edit, add fields:
Consider the information you need to store about the features you will be digitizing (i.e. type, name)
Name: no spaces, characters
Choose the correct field type
For text, edit length (max = 254)

13. The Editor Toolbar Options greyed out depending on feature type
Tools for creating or modifying features
Use to open the attribute window
Allows you to edit attributes for selected feature
Attributes can also be input into table directly

14. Making and Saving Edits
Editor toolbar, choose Start Editing from menu
Right-click layer, Edit Features > Start Editing
Saving your edits:
Choose Save Edits from Editor toolbar dropdown
Save often!! Unsaved edits will be lost forever!!!
Undo/Redo can be used until edits are saved

15. Drawing vectors Points are simple Lines can be straight, curved
Vertices and nodes, splitting
Polygons
Drawn using lines
Must be closed to be complete
Cut Polygon Tool (like splitting)

16. Digitizing
ArcCatalogue
File > New > Shapefile