1. GUS: 0265 Fundamentals of GIS Lecture Presentation 4: Raster Data Model and Operations Jeremy Mennis Department of Geography and Urban Studies Temple University

2. A raster representation is composed a series of layers, each with a theme Typically used to represent ‘field- like’ geographic phenomena Raster Data Model

3. Raster Resolution The distance that one side of a grid cell represents on the ground 1 22 4 4 1 1 4 4 1 1 2 4 4 1 2 3 3 3 3 2 2 2 2 2 = grid cell resolution The higher the resolution (smaller the grid cell), the higher the precision, but the greater the cost in data storage

4. Raster Data: ArcGIS

5. Data Compression Common Methods: –run length encoding –value point encoding –chain codes –block codes –quadtrees

6. Run Length Encoding and Value Point Encoding

7. Map Algebra and Cartographic Modeling A raster modeling language, and an approach to GIS analysis design, developed by J.K. Berry and C. Dana Tomlin in the late 1970s - early 1980s. It now forms the basis for grid-based analysis in ArcInfo (GRID and Spatial Analyst) and other GIS packages.

8. Map Algebra A set of formally defined manipulations on raster data. Operators: Fundamental mathematical and logical operations on raster data Functions: Complex combinations of operations

9. Functions: Types Higher order data manipulations on raster grids built from the more basic operators. Local: compute on single-cell basis Focal: compute on a neighborhood Zonal: use zones derived from a separate grid for evaluation Block: like zonal, but the result is assigned to an entire ‘block’ of cells Global: compute on the entire grid

10. Functions: Local – Single Values

11. Functions: Local - Mean

12. Functions: Focal – Immediate Neighborhood

13. Functions: Focal – Majority Min Mean

14. Functions: Zonal – Entire Zones

15. Functions: Zonal - Max

16. Functions: Global - Distance

17. Program Control: Statements and Programs Statement: notation to represent operations and functions e.g. NEWLAYER = LocalFUNCTION of FIRSTLAYER and SECONDLAYER Program: notation to represent a procedure; i.e. a sequence of statements in which each statement operates on the result of a previous statement

18. Program Control: Programs

23. Cartographic Modeling in ArcInfo: ModelBuilder Locating Suitable Sites for a Waste Dump

24. Cartographic Modeling in ArcInfo: ModelBuilder