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GUS: 0262 Fundamentals of GIS

GUS: 0262 Fundamentals of GIS. Lecture Presentation 6: Raster Data Model Jeremy Mennis Department of Geography and Urban Studies Temple University. Raster Data Model. A raster representation is composed a series of layers, each with a theme

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GUS: 0262 Fundamentals of GIS

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  1. GUS: 0262Fundamentals of GIS Lecture Presentation 6: Raster Data Model Jeremy Mennis Department of Geography and Urban Studies Temple University

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

  3. Regular Tessellations Squares Triangles Hexagons

  4. Irregular Tessellations

  5. Raster Grid • but most common raster is composed of squares, called grid cells • grid cells are analogous to pixels in remote sensing images and computer graphics

  6. 1 1 1 2 3 1 1 1 2 3 2 2 2 2 2 4 4 4 2 3 4 4 4 2 3 Raster Resolution The distance that one side of a grid cell represents on the ground = grid cell resolution The higher the resolution (smaller the grid cell), the higher the precision, but the greater the cost in data storage

  7. Raster Data: Encoding

  8. Raster Data: Encoding

  9. 1 1 1 2 3 1 1 1 2 3 2 2 2 2 2 4 4 4 2 3 4 4 4 2 3 Raster and RDBMS Raster layer can be attached to a RDBMS ID Land Use • 1 Agricultural • 2 Road • Residential • Industrial

  10. Raster Data: ArcGIS

  11. Raster Data: ArcGIS

  12. Raster in ArcGIS – Floating Point

  13. Raster in ArcGIS - Integer

  14. Converting Polygons from Vector to Raster

  15. Data Compression Common Methods: • run length encoding • value point encoding • chain codes • block codes • quadtrees

  16. Run Length Encodingand Value Point Encoding

  17. 1 1 1 2 3 1 4 4 4 3 2 4 4 4 2 4 4 4 4 3 4 4 4 4 3 Raster Chain Codes directions around the boundary of a region Value 4 North 1 East 1 North 2 East 2 South 3 West 3 Start

  18. 1 1 1 2 3 1 4 4 4 3 2 4 4 4 2 4 4 4 4 3 4 4 4 4 3 Raster Bock Codes two dimensional run length encoding 1 1 1 1 2 3 1 2 1 4 4 4 3 2 3 2 4 4 4 2 3 4 4 4 4 4 3 4 5 4 4 4 4 3 5 1 2 3 4 5 1 2 3 4 5

  19. Quadtree a partitioning of heterogeneous space into quarter sections

  20. Quadtrees • node is a quadrant that is heterogeneous • leaf is a quadrant that is homogeneous • quadrants are assigned an ID number according to their position and level

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