1. ©2005 Austin Troy. All rights reserved Lecture 3: Introduction to GIS Understanding Spatial Data Structures by Austin Troy, University of Vermont

2. ©2005 Austin Troy. All rights reserved Representation Entities Fields Bona Fide Fiat

3. ©2005 Austin Troy. All rights reserved Representation Entities Fields Vector Raster

4. ©2005 Austin Troy. All rights reserved Points (no dimensions) Lines, or “arcs” (1 dimension) or Areas, or “polygons” (2 or 3 dimensions) Vector

5. ©2005 Austin Troy. All rights reserved Raster Grids, or pixels Cell size is constant Area of each cell defines the resolution Raster files store only one attribute, in the form of a “z” value, or grid code.

6. ©2005 Austin Troy. All rights reserved Raster and Vector representations of the same terrain Raster: great for surfacesVector: limited with surfaces

7. ©2005 Austin Troy. All rights reserved Raster and Vector representations of the same land use:

8. ©2005 Austin Troy. All rights reserved Vector vs. Raster: bounding Raster: bad with bounding Vector: boundary precision

9. ©2005 Austin Troy. All rights reserved Vector vs. Raster: Sample points Cancer rates across space

10. ©2005 Austin Troy. All rights reserved Moving between vector and raster

11. ©2005 Austin Troy. All rights reserved WHEN TO USE RASTER OR VECTOR???

12. ©2005 Austin Troy. All rights reserved Raster and Vector Analytic advantage and disadvantages Technical advantages and disadvantages Specific Usages Tossups