1. UNIT 3 – MODULE 3: Raster & Vector

2. SPATIAL DATA MODELS *
A spatial data model represents real-world conditions within a GIS by relating geographic features.
There are two primary ways that data is modeled: raster and vector.
Learn More About Raster & Vector Map Data (2:26):
Credit: BiodiversityGIS

3. RASTER *
A collection of cells (pixels) that are organized into rows & columns, making up a grid.
Information is contained within each cell: location and value.
Satellite & aerial images are already formatted as a raster (e.g. thematic, surface and basemaps).
Raster Data Explained (6:07):
Credit: CUNY

4. VECTOR Made up of points, lines and polygons.
This model uses Cartesian coordinates (x,y) to store a spatial entity’s shape.
Points represent the simplest spatial entity, and lines connect points to form polygons
More complex line shapes mean more points are required to represent it.
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5. RASTER VS VECTOR *
Handout: Raster VS Vector:
Credit: Indiana University

6. MORE RASTER VS VECTOR Credit: www.landsurveyorsunited.com
Credit: City University of New York
Credit: Penn State

7. SPATIAL DATA STRUCTURE: RASTER
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8. SPATIAL DATA STRUCTURE: VECTOR
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9. RASTER PROS & CONS Advantage Disadvantage
Simplicity: data structures are simple, as are implementation of overlays.
Very efficient for image processing.
Disadvantage
Data structures are less compacted.
Topology is difficult to represent.
Feature boundaries & cell boundaries are not merged.

10. VECTOR PROS & CONS Advantage Disadvantage
Good at representing topology.
Can be adapted easily to scale changes.
Can be used easily with attribute data.
Disadvantage
Data structures are very complex.
More difficult to overlay data.
Difficulties with image processing.
Requires constant updating.