1. Raster and Vector Data

2. GIS data models
Raster model
Vector model

3. Raster types Thematic rasters Image rasters
Contain quantities that represent map data such as land use or rainfall
May be continuous or discrete
Image rasters
Contain satellite or air photo data

4. Thematic raster types Discrete data Continuous data
relatively few values
Values may change abruptly at boundaries
Continuous data
Thousands or millions of potential values
Values may change from cell to cell

5. Impact of resolution
90m resolution
Storage space increases by the square of the resolution
Portraying large areas at high precision is problematic
10m resolution

6. Vector model Polygon Vertices Line Points Nodes Y X
Features are stored as a series of x-y coordinates in a rectangular coordinate system.

7. Features linked to data
Each feature is linked to an entry in a data table containing information about the feature.

8. Advantages of vectors Precise location of features
Storing many attributes
Flexible for cartography
Compact storage of information
Ideally suited for certain types of analysis, especially areas, lengths, connections

9. Storage of attributes
Roads may have other attributes: ownership, speed limit, number of lanes, etc. Would need a new raster for each attribute. Only numeric attributes may be stored
Raster contains 1 value indicating a single attribute road type for example

10. Converting Vector to Raster Data is Easy

11. Converting Raster Data to Vector is Hard Nearly Impossible

12. Storing data in ArcGIS

13. In the vector world everything is a point, a line, or a polygon
Lines
Points
Polygons

14. Feature Classes
A feature class is a collection of similar objects with the same attributes, stored as a single unit.
Stored as spatial features with a table of associated attributes for each feature.
Because all features must share the same table, all must have the same attributes.
Feature classes may contain only one type of geometry (points or lines or polygons).
States feature class
Rivers feature class 14
Capitals feature class

15. Data formats
Coverages
Shapefiles
Geodatabases

16. Creating Shapefiles
To create a new shapefile: open ArcCatalog, right-click on a folder, click on New/Shapefile… in the drop down menu, enter the Name for the new shapefile, and then select the Feature type to be inserted. Optionally, you can also select the Spatial reference.
To add features to the shapefile, add the shapefile to an ArcMap document.

17. Shapefiles
A shapefile consists of multiple files, and the common ones are *.dbf, *. shp, *.shx, *.prj, *.avl, *.sbn
Shapefiles in Windows Explorer
Shapefiles in ArcCatalog

18. Shapefiles have a few parts:
"essential":
.shp: Shapefile geometry data
.dbf: database data
.shx: shapefile index (internal).
"important":
.prj: projection file with coordinate reference system info.
"other":
.sbn: shapefile (internal)
.sbx: shapefile (internal)
.avl: ArcView legend file
.rtf: data dictionary (rich text document)