UNIT 3 – MODULE 3: Raster & Vector

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): https://www.youtube.com/watch?v=aKdRiHezuk0 Credit: BiodiversityGIS

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): https://www.youtube.com/watch?v=VeI4n7duavI Credit: CUNY

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. Credit: www.lyzidiamond.com

RASTER VS VECTOR * Handout: Raster VS Vector: http://www.bokland.com/resources/RasterVectorInfo.pdf Credit: Indiana University

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

SPATIAL DATA STRUCTURE: RASTER Credit: www.innovativegis.com

SPATIAL DATA STRUCTURE: VECTOR Credit: www.innovativegis.com

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.

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.